“Metropolitan Parks” in Southern Barcelona: Key Nodes at the Intersection of Green Infrastructure and the Polycentric Urban Structure ^†

Abstract

Contemporary urban planning faces the ongoing challenge of developing Green Infrastructure capable of providing vital ecosystem services. Within this framework, the Barcelona metropolitan area has advanced a network of parks that, while serving local neighborhoods, also aim for metropolitan relevance. This study offers a forward-looking analysis of selected parks in the southern Llobregat River basin—an area shaped by historic villages and working-class settlements—to evaluate their contribution to both Green Infrastructure and the region’s polycentric structure. Building on previous landmark studies and multidisciplinary perspectives, the research examines eight parks through four spatial and scalar lenses, assessing their territorial role and accessibility, ecological connectivity, urban integration and permeability, and landscape design with both qualitative and quantitative data. Using a comparative framework alongside research-by-design methods tested in urban design studios, the research links analytical insights to design-based strategies. The outcome is a set of actionable guidelines aimed at enhancing local park performance, with broader implications for over 50 ‘Metropolitan Parks’ spread in more than 30 municipalities. These insights contribute to shaping a more integrated, livable, and resilient metropolitan region.

1. Introduction

In recent years, the Barcelona metropolitan area has been involved in discussions around its future development from a multidimensional standpoint [1]. A central objective has been to enhance its identity as a polycentric metropolis, grounded in the historic towns that make up the region. With this in mind, during the drafting process of the plan, it has been discussed what the elements and components of centrality in the 21st-century city might be, aiming to move from the basic notion of a center associated with historical cores to a more polysemic understanding of central places [2], thereby fostering a transition from a merely administrative polynuclear arrangement to a truly polycentric model. This involves going beyond administrative boundaries to promote genuine metropolitan dynamics.

In this regard, the idea of “Metropolitan Parks” [3,4] emerges as particularly relevant. This network consists of fifty-two distinct parks of different scales, located across thirty-four municipalities, and is envisioned to play a metropolitan role.

The designation “Metropolitan Park” was introduced by the Barcelona Metropolitan Authority (AMB), which, in addition to its responsibilities in urban planning, is also tasked with overseeing park policies and administration. Currently, the system of Metropolitan Parks centers around two major green areas: the Llobregat Agrarian Park and the Serra de Collserola Natural Park.

Apart from these large-scale green zones, the inherently polycentric structure of the Barcelona metropolitan area—formed by a constellation of municipalities with unique local identities—has fostered a variety of smaller green spaces. These parks, closely connected to each municipality, remain largely underrecognized at the broader metropolitan level. This situation continues despite several conceptual approaches, public policies, and initiatives over recent decades aimed at shaping a unified Green Metropolitan Matrix [5,6,7].

The Green Metropolitan Matrix, defined by Enric Batlle as “a set of public and private Green Infrastructures that can be developed on urban land or on undevelopable land and can be made up of spaces of widely varying form and origin” [8,9], is a framework that overlaps built-up and open spaces promoting both environmental and social values, a base for a cohesive Green Infrastructure system that articulates a new understanding between city and nature at every scale.

The main objective of this research is to explore the potential of these Metropolitan Parks not only to strengthen the region’s Green Infrastructure network but also to reinforce its polycentric urban structure. To achieve this, the study conducts an in-depth analysis of a sample of eight proximal parks, examining them through multiple spatial and functional lenses. This analysis aims to develop strategic guidelines that can be applied to other cases, emphasizing the metropolitan significance of these green spaces—not only in their ecological roles but also in their capacity to host and attract diverse urban functions.

By identifying key elements that contribute to both ecological connectivity and spatial cohesion, the study proposes ways in which these parks can evolve into multifunctional nodes that support a more cohesive and polycentric metropolitan fabric [10]. Ultimately, the research positions the whole of existing Metropolitan Parks in the Barcelona area as a collective opportunity: a system of green spaces capable of simultaneously enhancing environmental resilience and reinforcing a balanced, multifunctional urban structure across the metropolitan territory.

While public transportation has traditionally been central to metropolitan planning, the role of parks in this context has been less evident. Historically seen more as scenic elements than as spaces of intensity, parks have not always been recognized as key components of urban dynamics. However, they should be viewed as vital nodes within the Green Infrastructure—spaces that not only support ecological functions but also serve as recreational destinations for the 3.3 million residents of this densely populated metropolis, where access to green space is limited.

Within Barcelona’s city limits, residents have access to just 7 square meters of green space per person, excluding the more remote Collserola hills (the World Health Organization recommends the ratio to be 10 square meters), and only 30% of these green areas are open to the public [11]. In contrast, open spaces account for over half of the Barcelona metropolitan area, with more than 70% of residents living within a ten-minute walk from a park, according to AMB. This indicates a need for a stronger network of “Metropolitan Parks” to connect with a green-less center, as discussed in upcoming urban policy [12]. Recent municipal and metropolitan initiatives such as the Barcelona Green Infrastructure and Biodiversity Plan 2020 [11], and the Pla Natura Barcelona 2021–2030 [13], in line with similar European efforts, aim to expand and enhance the city’s green spaces. These initiatives aim to transform underutilized open spaces into fully functional urban parks, with the potential to evolve into a network of interconnected green areas that deliver ecological services on a metropolitan scale.

In this regard, it is necessary to consider the origin of Barcelona’s parks, as their configuration is an example of a non-capital European city where the absence of parks inherited from former royal or aristocratic estates led to various civic initiatives aimed at providing open spaces for public recreation and balancing the intensity of urban life. As early as 1859, Ildefons Cerdà’s well-known expansion plan incorporated a generous and diverse provision of public spaces, ranging from gardens to a large forest area along the Besòs River. However, most of these were never realized due to management challenges and the lack of legal tools for land acquisition [14].

Even so, collective initiatives played a key role in securing two major parks for the city, taking advantage of the momentum generated by two major international urban events: the 1888 Universal Exhibition in Parc de la Ciutadella, and the 1929 Exhibition, which marked the initial development of Montjuïc hill [15]. The well-known Park Güell, with its layout, infrastructure, and pavilions designed by Antoni Gaudí in 1903 for a garden-suburb development, was acquired by the municipal government in 1926 and turned into a public park. By the 1920s, architect and landscape architect N.M. Rubió i Tudurí, responsible for planning and designing open spaces for the city, had already proposed an advanced and systematic vision of open space, organized into concentric rings (inner parks, suburban parks, and outer parks). His approach recognized the environmental value of the large forests surrounding the city as a key contribution to the urban and metropolitan environment [16].

Among Barcelona’s notable hallmarks in park-making, and directly tied to the following research, is also the period when the first democratic city councils (starting in 1978) promoted the creation of modern urban parks throughout the city. These initiatives capitalized on available opportunities: reprogramming obsolete facilities (Parc de l’Escorxador in 1982, Parc del Clot in 1986), developing vacant interstitial areas on the city’s early periphery (Parc de la Creueta del Coll, 1981–1987), or repurposing former industrial spaces (Parc de l’Espanya Industrial in 1985, Parc de la Pegaso in 1986) [17].

Since then, the city has undergone a significant shift in scale: from a compact city bounded by natural barriers (the sea in front, mountains behind, and a river on each side) to a multicentric metropolis. This new metropolitan constellation is made up of formerly independent smaller cities orbiting the mother city. In this interconnected territory, open space takes on a central role: not only in terms of quantity, but also as an opportunity to shape a balanced, equitable, and sustainable metropolis.

1.1. Historical Background: Green Spaces and Connectivity in Urban Planning

The parks examined in this research should not be understood as isolated entities, but as integral components of a complex system that also includes a wide variety of open spaces. Systemic configurations of this kind, varying in form and scope across cities and contexts, are increasingly recognized as fundamental structural components of the metropolis and as key tools in its strategic planning and transformation [18]. More specifically, the improvement of connectivity among green open spaces in metropolitan areas has long been considered a strategic objective in urban and landscape planning. The creation of an interconnected matrix of parks, greenways, and promenades—where vegetation either dominates or could be enhanced—has been a well-established approach, with proven benefits for urban form, ecological performance, and quality of life.

One of the earliest and most influential conceptualizations of the “park system” can be traced back to the work of American landscape architect Frederick Law Olmsted in the late 19th century [19]. In cities such as Buffalo (1868) and Boston (1878), Olmsted proposed connecting existing parks through tree-lined boulevards or transforming underused plots into public green areas [20]. These early systems anticipated many of the advantages later associated with green infrastructure: the creation of continuous and accessible green space, the extension of park influence to broader populations, and the integration of green areas of varying sizes and types, including the potential to link urban and rural landscapes. Olmsted’s example, and his influential model of green space connectivity, has since inspired other notable plans, such as the 1906–1909 Plan of Chicago by Burnham and Bennett [21]. In Kansas City, Missouri, a series of projects by urbanist and landscape architect George E. Kessler (completed in the years 1893, 1909, 1915) created a green corridor network linking parks, gardens, and natural reserves shaped by geographical features [22]. This case compellingly demonstrates how a well-designed green space system can structure and clarify the urban layout as a whole.

From the United States, the idea of open space systems as constitutive elements of a well-balanced metropolis was transferred to urban and regional planning in Europe, where it took on diverse and context-specific forms: a Metropolitan Green Belt for Greater London (1919); a ring of peripheral parks connected by an amoeba-shaped expanse of forests and farmland in Martin Wagner’s General Open Space Plan for Berlin (1929); Green Wedges between urban ‘Fingers’ in Rasmussen’s Copenhagen (1947); a Green Heart for the Randstad-Holland; or a structure composed of countless heterogeneous elements in the Ville Poreuse analogy for Grand Paris (2009), among other examples.

The early intuition of pioneers like Olmsted and Kessler anticipated the value of continuity in green space networks long before ecologists demonstrated that interconnected ecosystems are significantly richer, more biodiverse, and more resilient than isolated ones. Drawing on such findings, and thanks to the influential dissemination efforts of scholars like Richard T.T. Forman [6,23], landscape ecology has emphasized the importance of preserving ecological corridors to maintain biodiversity flows, a key factor in ecosystem health.

The integration of ecological knowledge into urban planning has also progressed through internal developments within the discipline. The influence of ecological thinking gained traction, among other contributions, through the teachings of architect Ian L. McHarg at the University of Pennsylvania from the late 1950s onward. McHarg argued that natural systems and processes operating within the land constitute a valuable form of social capital that should be preserved, or even enhanced, and that urban development should be designed in accordance with these processes, reconciling nature and the built environment [24].

Building on these seminal contributions, the importance of connectivity among open spaces as a positive attribute for spatial order and metropolitan balance has been widely theorized [25]. Moreover, in recent years, a growing body of research has emphasized the role of landscape connectivity in climate change adaptation, underscoring its capacity to facilitate ecological resilience and adaptive responses to environmental transformations ([26,27]).

1.2. Metropolitan Parks: From Green Infrastructure Components to Inclusive Social Catalysts

Calls to action on a supra-national level, such as those by the European Union [28], have fueled the discussion around the topic of Blue and Green Infrastructure, advocating for their implementation in order to secure key ecosystem services [29] and to protect natural capital in the sustainable growth of cities. Recently, the new European Green Biodiversity Strategy 2030 [30] has reinforced this position, as the promotion of healthy ecosystems is linked to the development of Green Infrastructure and nature-based solutions (for example, via the enlarging of the Natura 2000 areas), interlinked via an integrated approach in planning and design counter to the increasing fragmentation of natural areas at the tail-ends of the metropolis caused by peri-urban growth.

In response to the call for Green Infrastructure, European countries have introduced a range of paradigms, each with distinct interpretations [31,32]. These strategies vary widely, from large-scale regional approaches, such as the Ruhr metropolis [33], to initiatives in major capitals like Paris, which seek to rework urban density [34]. Meanwhile, “Mediterranean approaches” address the pressing challenges of climate change.

Cities like Milan [35,36], Turin [37], and Barcelona [38] have embraced more distributed and integrated Green Infrastructure plans, incorporating diverse ecosystemic spaces, including agricultural areas near the urban core. Examples include Barcelona’s Parc Agrari and Milan’s Parco Agricolo Sud [31], which safeguard valuable foodscapes from urbanization. Additionally, these plans focus on restoring natural waterways by reducing reliance on rigid grey infrastructure, which often constrains river width and diminishes flood mitigation capacity, key factors in managing sudden flooding.

However, green and blue infrastructures do not exclusively refer to biodiversity and resilience, as at the same time they can be helpful in the improvement of inhabited areas, catering to social needs as much as ecological ones. Green Infrastructure offers the chance to improve social and economic conditions [39]: environmental benefits derived from improved public spaces also grant better accessibility to these spaces, as they become more cohesive meeting spaces, which in turn become part of a wider large-scale network. The distribution of Green Infrastructure over the cityscape is mostly guided by large-scale natural elements, cutting across administrative boundaries. This offers a change to rethink “unfinished” boundaries, connecting fabrics via a multi-scale, metropolitan, scope. In this way, an over-arching system of green space help guide interventions that re-connect formerly divided dense neighborhoods, such as through the re-purposing of grey infrastructures, integrating green canopies at street sections, or rethinking the design of large open spaces and parks. Despite the complex challenges of working with what is already built, it is a chance to link strategic considerations with local needs.

In this regard, Barcelona’s Metropolitan Authority has stated that it aims to “re-naturalize the territory and enhance the values of its biophysical matrix, rebuilding the metropolitan green and blue infrastructures to ensure their continuity, and incorporating into them all areas with environmental value, thereby reinforcing their ecosystem functions” [40]. With this overarching goal, the interventions carried out over the past decade aim to weave a network composed of a series of nodes or “structuring parks” interconnected by a system of “green corridors” (Figure 1).

This research builds on past local landmark reports and multidisciplinary studies that examine Green Infrastructure within the context of Barcelona’s metropolitan area [4,12,40], of which Forman’s “Mosaico territorial para la región metropolitana de Barcelona” [41] is an important highlight, as it set the basis for the city’s main green elements. It also references international experiences that advocate for “constellations of parks” [42] and evaluate the importance of linking-up urban green parks [43,44,45], as this research examines the potential interrelation of a series of parks as seen through eight case studies in the Llobregat Basin (Figure 2). This area, threatened by urbanization, has a significant role in mitigating the heat of the urban core, providing an important modulator for temperatures within the city, as its green spaces provide ecosystemic services relevant to Barcelona’s climate, cooling nearby neighborhoods, moderating the impact of stormwater and significantly improving the air quality of the city. Edging ever forward towards them, a series of towns, now part of Barcelona’s metropolitan area, urbanize the Llobregat valley at equal intervals, though with different conditions depending on each of the river’s sides. Within these municipalities, a series of local parks hold the potential to be integrated within a wider, metropolitan network of green spaces, linking urban and natural spaces.

Regarding these parks, previous reports co-developed by the Area Metropolitana de Barcelona and Barcelona Regional (BR) already provide a synthetic overview, with precise individual profiles, based on the locally developed concept of “socio-ambiental services”, which has been in use since a decade ago [3], and balances natural and social benefits. These reports offer a case-by-case quantitative assessment of their general characteristics, ecological factors, environmental quality, metabolic processes and public use, with data collected from field studies, satellite imagery and institutional databases.

Grounded in contemporary socio-ecological concepts that promote parks as inclusive social catalysts [44,45], this study investigates their internal composition to reveal interactions between programmed and unprogrammed spaces. Leisure areas, public facilities, sports centers, and playgrounds intersect with forests, meadows, and shrublands, creating a hybrid ecological matrix that fosters new public spaces. These small-scale intersections are considered integral components of a polycentric network of green nodes, in turn examined in detail. This approach aims to enhance equitable access to green spaces [46,47] while recognizing the role of medium- and large-scale natural areas embedded within diverse urban forms.

2. Materials and Methods

Research on potential “Metropolitan Parks” is performed through the analysis of a series of case studies of parks in the process of shifting towards a growing metropolitan condition from its former local and peripherical character; by highlighting their current qualities and by recognizing their potentialities, their role to play in the future city can be established, protecting them from uniform landscape design solutions. Some pre-requisites have been considered in order to define them, such as (1) being on public land and open to the general public; (2) having “green” as a main element in its internal composition; (3) being programmed for diverse collective uses, related to leisure. If the previous conditions are common to any park, their metropolitan nature derives from a dual affiliation: their connection to contemporary urbanization trends, and their conceptual relevance as the focus of present discussions.

2.1. Metropolitan Parks

Regarding its role in contemporary urbanization, the Metropolitan Park contributes to the system of open spaces, which, in today’s metropolises, hold significant quantitative weight in land area and the capacity to organize, structure, and equip the city. This stimulates a renewed relationship between the “countryside” and the “city”. Positioned on a growing periphery, the Metropolitan Park must have a minimum extension to serve a meaningful function in this context. This size should have a qualitative aspect: it should provide a certain sense of contact with nature, allow for picturesque aesthetics, encourage diverse spaces and facilities, and evolve into an authentic environmental unit, making its management and maintenance more sustainable.

It is also essential that the park has effective accessibility through a variety of mobility systems, enabling it to serve beyond just the local community. To ensure its metropolitan-level service remains attractive, the park must offer a wide range of services and amenities, including some more or less exclusive attractions.

2.2. Scales of Analysis and Research Approaches

Owing to their trans-scalar condition, and in order to study the aforementioned concepts, the research has considered four different scales of analysis:

• Territorial Role within Metropolitan Networks, 20 × 20 km scale: This scale allows for an understanding of the park’s position within the metropolis as a whole and, specifically, its relative position concerning the networks that provide its functional support (transport infrastructure, collective communication systems, metropolitan-scale public facilities, etc.). The graphic analysis sources materials from the “Pla territorial metropolità de Barcelona”, selecting a series of rail infrastructures to study based on publicly available CAD data. Furthermore, the basemap has been sourced from the “Cartografia Bàsica AMB”, and has been edited to highlight each of the case study parks, with a table relating travel times from the park to key urban centers with information sourced from Barcelona’s Transport Authority [4].
• Land cover and green connectivity, 3 × 3 km scale: This scale relates the park’s public space to the system of nearby metropolitan open spaces, enabling an understanding of the park’s actual or potential contribution to the ecological systems and processes operating within the bio-physical matrix that supports the metropolis. A GIS graphic analysis has been made based on selected layers of the land cover map of the Institut Cartogràfic de Catalunya (Barcelona, Spain), as well as data sourced from Barcelona’s Metropolitan Authority AMB. Where data were not covered by AMB’s studies, data were obtained by recreating AMB’s methodology, keeping the values consistent with the study’s original timeframe (2021) so as to establish comparisons between parks. Key parameters of each of the parks are included, indicating the proportion of green within a 3 × 3 km buffer sourced through the aforementioned land cover map and processed with QGIS 3.40. In this regard, the average NDVI value of each of the parks in 2021 was sourced via satellite imagery provided by Sentinel-2 (ESA, Paris, France), and processed using QGIS. The biodiversity level of each the parks was derived via the Shannon index, sourced from a study published by AMB [4]. Finally, an analysis of each of the parks in relation to large green connectors measures the position of these structures via QGIS and land cover data.
• Urban fabric and perimeter definition, 2 × 2 km scale: This scale provides a perspective on the park’s immediate surroundings, examining the urban fabric that encloses the open space and how its particular morphology influences the formal and functional response of different areas within the park. Vector data on build-up areas provided by the Institut Cartogràfic de Catalunya were used to relate each of the parks to their surroundings through QGIS in a 2 × 2 km area, alongside population data sourced from census data [48]. Thermoregulation data, sourced from AMB [4], were recreated via satellite data obtained from Landsat (NASA/USGS, Washington, D.C., US, Reston, VA, US) through an LST study comparing the average surface temperature of the park with that of areas surrounding it via QGIS and Google Earth Engine [49]. Finally, individual gross incomes within close proximity of the park have also been sourced from AMB and further completed with census data in regard to Park Three [4,48].
• Park Design, 1 × 1 km scale: This level delves into the park’s composition, examining its layout, components, dimensions, functions, equipment, and overall design. Data obtained from in situ visits have been contrasted with information obtained from high-resolution orthophotos provided by AMB, which have been used as a base to develop a CAD-based graphic study of each of the park’s internal compositions and design elements. The case study parks have been entirely redrawn and measured, classifying each of the surfaces in relation to their surface composition in a series of categories that range from the urban to the natural.

At all these scales, the Metropolitan Park project can play a role in contributing—within its possibilities—to the creation of a more balanced, diverse, just, and sustainable metropolis. At each scale, every case study may gain valuable insights from the specific responses of other cases [50]. This is the approach taken: analyzing cases and scales to highlight the qualities of each park and envision its potential for future improvement.

Complementing the multiscalar analytical framework, this research also adopts a research-by-design approach to identify opportunities for improving the metropolitan role of local parks. Several scholars have highlighted the value of integrating design into spatial research, arguing that the design process itself is a vehicle for knowledge production -especially when it is used not just to plan, but to probe the possibilities embedded in spatial contexts [51]. This is particularly relevant for open-ended or future-oriented planning challenges, such as those posed by environmental change. In this regard, various authors [52,53] position research-by-design as a fitting method for dealing with indeterminate conditions and complex systems, consistently placing design at the core of the exploratory process to unlock the spatial and functional potential of each site.

In relation to this study, this approach is especially suitable for envisioning spatial strategies that are developed and tested across different scales. This iterative, creative process enables the identification of context-sensitive solutions—not through a linear or object-oriented logic, but by embracing the speculative and synthetic nature of urban design [54].

2.3. Case Studies: Eight Parks in the Llobregat Basin

The lower Llobregat valley represents a geographically asymmetric area: the river acts as a dividing line, with denser urban development concentrated on its eastern (left) bank, while the western (right) side features lower urban density and more prominent natural landscapes.

Eight parks (see

Table 1. Number, name, municipality and area of the parks.

Number	Park Name	Municipality	Area (ha.)
1	Pi Gros	Sant Vicenç dels Horts	27.5
2	Can Lluc	Santa Coloma de Cervelló	8.9
3	P. Cripta Güell	Santa Coloma de Cervelló	5.7
4	La Muntanyeta	Sant Boi de Llobregat	29.7
5	Torreblanca	Sant Just Desvern	11.7
6	Fontsanta	Sant Joan Despí	29.0
7	Can Mercader	Cornellà de Llobregat	25.1
8	De Les Planes	L’Hospitalet de Llobregat	8.3

) were selected across both sides of the valley for their representative spatial configurations: they are experiencing the shift towards their metropolitan condition at different speeds, showcasing different elements of this process, owing to their proximity to urban and natural elements, and connection to wider green and transport infrastructures, but also in relation to specific leisure and cultural programs such as sports centres, museums, ornamental gardens and other identifying traits of their internal composition.

The definition of the park’s boundaries is defined by these aforementioned identifying characteristics, either porous or strict as the parks continuity with other elements is examined, rather than considering the strict and arbitrary administrative perimeter of the park itself. Their sizes can be divided between two groups: those with a surface area between 5 and 12 ha, and those with a surface area between 25 and 30 ha, and feature areas comparable to well known “central” parks of the city of Barcelona, such as Park Güell (17.18 ha) and the Ciutadella Park (17.42 ha, 31 ha including its zoo).

As such, urban parks such as those in the left margin are well defined and enclosed by built-up surfaces yet made complex by the presence of hybrid leisure activities compatible with the usual program of a park. On the other hand, those in the right margin, though also featuring a cohesive value that identifies them, also often feature undefined margins that connect them with green structures of a larger order.

Three approaches are considered regarding the several case studies and their relationship with their surrounding urban and natural environment: (1) that of their link with the central city of Barcelona, yet not as mere peripherical components, but as elements that connect the urban core with Green Infrastructure components, such as the Ordal mountain park and the Llobregat river systems; (2) as an inter-connected network of parks that acquires a higher dimension than the individual parks themselves, linked by public transportation, allowing them to offer complimentary services to each-other, adding complexity to the park’s program through specialization, in turn adding interest to a particular park beyond its former local character; (3) as complimentary green centers joining local nodes, connected through a series of green promenades offering a park-like perception in the approach towards them, in this way reinforcing the ecosystemic services provided within the urban fabric.

2.3.1. The Western Side of the Llobregat River Basin

This side is defined by the Serra de l’Ordal, a mountain range that stretches across multiple municipalities. It shapes a landscape where green areas—more modified near urban edges—link the agricultural lands of the Llobregat Delta, the river basin, and surrounding forests, with minimal disruption from roads or railway lines. Parks here retain a largely natural character [55], but their peripheral locations and low population density limit their potential as metropolitan hubs.

Four selected parks are located on this side:

• Pi Gros (1)—acts as a potential ecological “bridge” between the Serra de l’Ordal and the Llobregat Basin. Positioned near railway lines, its porous surface—composed of woodland and shrubland—forms part of a broader Green Infrastructure system.
• Can Lluc (2)—located on the outskirts of Santa Coloma de Cervelló, reflects its transitional position. Near the town, it features urban elements like playgrounds and parking, while further out, it shifts into meadows and forested zones, creating a gradient between built and natural environments.
• Cripta Güell (3)—surrounds the renowned Cripta Güell, a heritage site designed by Antoni Gaudí. Although not managed by AMB, it holds cultural significance. The park is characterized by pine trees interspersed with remnants of unused building materials from the church’s original construction.
• La Muntanyeta (4)—presents a dual landscape: its lower area is urbanized, integrating civic buildings like municipal offices, libraries, sports centers, schools, and a swimming pool. Its upper part, defined by rugged topography, consists of shrubs, open meadows, and woodland.

2.3.2. The Eastern Side of the Llobregat River Basin

This side is heavily urbanized, with fragmented green spaces disrupted by transport infrastructure. The ratio of open space to built-up area is roughly half that of the western side [2]. Parks here are more modified by human activity and are subject to intense recreational, functional, and ecological demands.

Four case-study parks were chosen here, as outlined below:

• Torreblanca (5) is in an urban setting and close-by to the Joan Gamper sporting facilities. It is an amalgam of several green spaces: a nineteenth-century ornamental garden from a private origin, a dense and orderly green canopy, some fields regularly planted with ornamental purposes and two small ponds with adjacent open spaces punctuate the park. Furthermore, the original palace of the historic garden and some new buildings host some public administration offices.
• Fontsanta (6) is a large, highly urban park that is well integrated into the metropolitan fabric. It is adjacent to major facilities like the regional public television station and a large hospital, as well as local community services.
• Can Mercader (7) is divided by steep terrain and rail infrastructure. The southern portion is an ornamental 19th-century park centered around the historic Can Mercader house—now a mathematics museum. The northern section, with its winding paths and meadows, is disconnected and more topographically complex.
• Les Planes (8) lies beside the densely packed Cemetery of Hospitalet and is situated within one of the most densely populated areas in Europe [56]. Its layout is highly structured, segmented into zones for play, sports, leisure, and parking, with actual green space confined to the park’s edges.

3. Results

3.1. Territorial Role Within Metropolitan Networks

In regard to the territorial scale, where large-scale natural systems are developed in Green Infrastructure plans (see Figure 1), the relationship between open spaces and their accessibility is not as direct.

The topic of accessibility has special significance in the link from local to metropolitan. The street space is determined by the articulation of public spaces, as qualitative elements such as well-designed sidewalks, building interesting scenarios that accompany movements between nodes (parks, train stations) [57]. These small-scale connections link up with the metropolitan scale through rail infrastructure, as a good public transport network can determine the park’s potential in reaching beyond their local role. Regarding this topic, the selected case studies examined present an interesting configuration in relation to the rail transit network and the different urban nodes near the parks:

• The western margin of the Llobregat presents an almost perfect overlap between suburban rail stations and selected case studies, owing to an often-occurring triple intersect between park–urban center–train station considering the development of this margin through independent townships (a configuration that lends itself well to the aims of the multi-center metropolis envisioned by the future Barcelona PDU Masterplan).
• The eastern side is much more integrated both within the urban fabric and the transportation network, with inter-connected tram, metro and rail lines of different scales.

Figure 3 provides a spatial overview, mapping the parks’ positions and nearby public transport in a 20 km × 20 km area. Most parks are less than a ten-minute walk from a station. These transit lines connect them to major urban nodes and transport hubs like Plaça Espanya and Plaça Catalunya, with commute times ranging between 15 and 45 min (see

Table 2. Time to nearest station and Plaça Espanya (walking, train, bus, referring to “W, T, B”).

Number	Park Name	Nearest Train Station	To Pl. Espanya
1	Pi Gros	6 min (W)	35 min (W + T)
2	Can Lluc	5 min (W)	30 min (W + T)
3	P. Cripta Güell	6 min (W)	29 min (W + T)
4	La Muntanyeta	14 min (W)	26 min (W + B)
5	Torreblanca	7 min (W)	42 min (W + B + T)
6	Fontsanta	3 min (W)	37 min (W + T + T)
7	Can Mercader	8 min (W)	22 min (W + T)
8	De Les Planes	2 min (W)	14 min (W + T)

). Parks One to Four and (Can Mercader) on the western side are linked via the FGC line to Plaça Espanya and onward to Plaça Catalunya. On the eastern side, Parks Five and Six connect directly to the metro system, which also serves Parks Seven and Eight, ensuring access to intermodal facilities and the wider metropolitan area.

3.2. Land Cover and Green Connectivity

A study of non-urban land cover near the parks reveals the differences in the context of the case studies and their continuities through green spaces. The connections, still partly unfulfilled, hold the potential to enhance the metropolitan Green Infrastructure system (Figure 4). On the western side, Parks 2 and 3 can be seen as open spaces in the middle of urbanized areas that, nevertheless, serve as unintended ecological connectors between mountain ranges and the river corridor thanks to their key position. For example, Parks One and Four are located on elevated terrain near the valley and interface with open, higher-altitude ecosystems. These sites offer opportunities to extend ecological corridors into more urbanized zones.

On the eastern side, by contrast, Parks Five to Eight are immersed in a largely urbanized context. This circumstance enhances the value of their own large surface, as unique and attractive places. Even so, it is worth considering the possibility of extending their influence by improving civic connections to nearby open spaces. In all four cases, the proximity or close contact with grey infrastructures and their leftover perimeters suggests the possibility of regenerating them via greening strategies so as to extend the influence of the parks’ service.

Regarding the data of

Table 3. Land cover and green connectivity parameters.

N.	Proportion of the Park’s Green Space Within a 3 × 3 km Buffer	Intensity of Green (NDVI), 0–1. Authors, [4]	Biodiversity Index (Shannon Index), 0–3. Authors, [4]	Distance Between Park and Large Green Connector (m)
1	7%	0.90	2.48	0
2	1%	0.85	1.9	0
3	1%	0.51	-	0
4	9%	0.78	2.2	50
5	4%	0.65	2.9	600
6	17%	0.72	3	1100
7	16%	0.8	1.2	1200
8	4%	0.62	2.5	1400
Av.	7%	0.73	2.3	540

, a series of variables have been considered in order to determine how each of the parks relates to its surrounding green spaces:

A Normalized Difference Vegetation Index study (NDVI) is employed, with values ranging from 0 to 1. This commonly used method determines the quality and intensity of green spaces, and reveals that parks closer to natural areas feature a much more intense and green character, although the Parc de Can Mercader’s lush ornamental gardens also feature high figures despite its urban environment. Regarding biodiversity, the Shannon index applied by AMB [4] is referenced. This index, a mainstay of biodiversity studies, indicates with higher values indicate greater diversity, meaning the park has a good mix of species and relatively even distribution. Lower values suggest that either fewer species are present or one or two species dominate. In the case studies, AMB indicates that Parks Five and Six feature the highest diversity, despite being located in dense urban areas, whereas Parks Two and Seven are not diverse in relation to number of species, though their values are still higher than parks closer to more urban areas within Barcelona itself.

The proportion of each park in relation to a 3 × 3 km buffer shows how large parks within urban areas represent an important percentage of green within dense neighborhoods, whereas both smaller urban parks and parks beside natural areas are not as determinant. The parks on the western side generally account for a very small percentage of the unoccupied land within their area of influence. This aligns with a common urban context characterized by fragmented development and closer proximity to the river system (as distances to any large-scale open space range from 0 to 50 m). Among these, Parks One and Four have slightly higher percentages due to their larger surface area. On the eastern side, the percentages of unoccupied land tend to be higher, given the more continuous urbanization that distances the parks from large-scale open spaces (between 1100 and 1400 m, except for Park Five. However, Park Five stands out for its lower percentage due to the closer proximity between the river and the mountains in this area, while Park Eight also has a lower percentage due to its more modest surface area.

3.3. Urban Fabric and Perimeter Definition

The morphology of the urban fabric around the parks, in square areas of 2 km sides, shows a quite heterogeneous picture. It is possible to characterize different sections of the perimeter of each park, according to changes in adjacent urbanization (more or less occupied, intense, connected to the city layout, etc.). Ultimately, many of the parks present the same condition: they are open spaces surrounded by city fragments with different morphology (see Figure 5).

Park Eight, surrounded by similarly dense urban fabric on all sides, contrasts with Park Four, which borders compact, high-density development to the east and more dispersed, lower-density zones to the west. Park Seven sits in between its eastern edge shaped by residual spaces from road infrastructure, with denser residential development to the north and south.

Furthermore, the role of the park as a place of transit is implicitly seen by two close-by urban fragments separated by the open space. While in Park Two, the low intensity of urbanization in the northern part does not suggest that the transversal flows should be attended to, in Park Six, the park seems to require attention to this need for connection between the urbanized fragment to the north and the more continuous city to the south.

Regarding the parametric study of

Table 4. Parametric data of urban areas adjacent to each park.

N.	% of Built-Up Areas within a 2 × 2 km Buffer	Potential Inhabitants in a 15 m Walking Buffer. Authors, [4]	Thermoregulation, Average Temperature 15 min Away from a Park/Average Temperature of a Park. Authors, [4]	Individual Average Gross Income within 500 m. Authors, [4]
1	18%	19,000	0.8	EUR 14,000
2	6%	4000	0.9	EUR 18,000
3	7%	800	0.9	EUR 16,500
4	28%	20,000	1.48	EUR 11,500
5	24%	41,000	0.9	EUR 15,000
6	30%	58,000	3.48	EUR 22,000
7	34%	61,000	2.48	EUR 13,500
8	40%	135,000	0.75	EUR 12,500
Av.	23%	63,725	1.46	EUR 15,375

, it is worth highlighting the extreme case of Park Eight, where high land occupation corresponds to the highest population density, given the area’s high-density housing for moderate-income residents. Notably, the park’s thermoregulatory effect is low despite its potential impact on a dense and active area, likely due to the relatively small size of the open space. At the other end of the spectrum, Parks Six and Seven exhibit a high thermoregulatory impact, as they combine a significant open space area with relatively high land occupation and population density. Park Five falls into an intermediate category, showing a low thermoregulatory capacity despite being in a densely populated and relatively occupied environment. This can likely be attributed to the park’s modest size and the presence of other nearby unoccupied spaces.

Meanwhile, Parks Two and Three are situated in areas with very low urban occupation, meaning their moderate thermoregulatory capacity should not be considered a negative aspect.

3.4. Park Design Qualitative Considerations: Urbanization Versus Naturalization

The design of the parks themselves produces an important complementary perspective. This lens, given by study of the internal composition of the parks, characterizes the different surfaces by type and allows comparisons in terms of landscape, degree of urbanization and imperviousness, preponderance of programmed leisure uses, etc.

The approach of these projects, as well as those yet to be developed, aims to contribute equally to citizens’ quality of life and the health of ecosystems. Interventions are carried out in spaces of varying scales, with greater emphasis placed on the systemic and infrastructural nature of the actions. Restorative landscape practices are employed, tailored to the specific characteristics of each site—such as planting native or low-water-demand species—applying ecological and environmental sustainability criteria, and seeking a fair balance between the benefits provided by vegetation and the resources it consumes [58].

These criteria align with the emerging typology of parks that has developed worldwide since the turn of the century, as outlined by Cranz and Boland [59]. Ultimately, as acknowledged by the metropolitan authority of Barcelona responsible for their planning and management, the concept of the park in the 21st century has expanded. It is no longer confined to enclosed areas; instead, alongside historical open spaces, there now exist more open and flexible spaces: a network of peripheral parks aimed at connecting the various parts that make up the metropolis, filling in the gaps with nature and planting in all kinds of interstitial areas. The goal is to reduce the qualitative gap between the center and the periphery and to promote the presence of vibrant spaces capable of supporting native ecosystems, while also encouraging civic activity and contributing to social cohesion [58].

The spatial distribution of different land cover types—such as wood, meadow, scrubland, urbanized areas, etc.—and the resulting patterns are key factors in understanding each park, assessing its suitability, and identifying opportunities for improvement (see Figure 6).

Parks One and Six feature singular types of landscape patterns, but totally opposite: Park One has a highly natural character and Park Six is completely artificial and designed. On the other hand, Parks Four, Five and Seven result from a combination of different types of spaces with particular compositions. “Ornamental gardens” are joined with nature-inspired landscapes, as well as fragments of contemporary designs and other urbanized spaces that include public facilities or playgrounds and sports areas. In the end, each park is formed by bringing together, in a singular composition, different spaces, forming places of synthesis between nature and artifice. An analysis of each park’s internal structure reveals current limitations, but also highlights latent opportunities for enhancing functionality, connectivity, and identity as part of the broader metropolitan Green Infrastructure.

Park Design Quantitative Dimensions

Quantitively analyzing the surfaces dedicated to the different types provides further topics for comparison (see

Table 5. Surface distribution of the parks.

N.	Woods		Meadow		Scrubland		Water		Paths and Urbanized Areas		Playground		Built-Up		Parking Lots		Total (ha.)
1	12.6	46%	0.7	3%	8.8	32%	0	0%	3.0	11%	0.7	0.3%	2.2	8%	0.6	0.2%	27.5
2	2.3	26%	2.3	26%	1.8	20%	0	0%	1.8	21%	0.3	3%	0	0%	0.4	5%	8.9
3	2.6	45%	0.3	6%	0.8	14%	0.05	0%	0.9	15%	0.6	10%	0.2	3%	0.4	7%	5.7
4	5.9	20%	6.4	22%	4.6	15%	0.5	2%	7.0	24%	3.3	11%	1.1	4%	0.9	3%	29.7
5	4.3	37%	2.0	17%	0.7	6%	0.4	4%	3.2	27%	0.2	1%	0.3	2%	0.6	5%	11.7
6	2.2	7%	5.9	20%	6.1	21%	0	0%	10.2	35%	1.6	5%	1.3	4%	1.9	7%	29.0
7	7.1	28%	5.8	23%	1.9	7%	0.3	1%	7.8	31%	1.1	5%	0.6	2%	0.4	2%	25.1
8	2.0	24%	1.5	18%	0.1	1%	0	0%	3.2	39%	1.1	13%	0.1	1%	0.3	3%	8.3
Av.	4.1	29%	3.7	17%	4.3	14%	1.4	1%	4	25%	2.2	6%	1.4	3%	2.9	4%	11.3

and Figure 7). Based on their natural areas, Parks One, Two and Three stand out due to the preponderance of vegetation, whereas Parks Four, Five and Seven present a balanced distribution. Parks Six and Eight do not feature a large proportion of natural spaces in comparison with urbanized, programmed or built-up surfaces. The vegetation within each park is distributed among tree canopy, grasslands, and shrubland, with the specific ratio of these elements defining the park’s overall landscape character.

In terms of urbanized surfaces, the parks located on the eastern side tend to have a higher proportion. This may be linked to the greater demand for recreational and functional spaces in these more densely built-up and active urban environments.

Looking at the designated or programmed areas, several distinctions can be observed. The intensity of use varies across parks: Parks One, Two and Seven show lower levels of occupation, whereas Parks Four, Six and Eight display higher degrees of use. Additionally, the mix of functions and activities within these programmed spaces differs in both variety and proportion, contributing to the unique profile of each park, as Park One presents a few notable built-up spaces and Parks Two, Three and Six show a significant amount of parking space, whereas Parks Four, Five, Seven and Eight are more diversified, albeit Park Five’s playgrounds are not as prevalent as in other cases.

4. Discussion

The sample of 8 parks in the Llobregat Area proves to be significant in relation to the set of more than 50 parks that characterize the Barcelona Metropolis. Their representativeness is evident in terms of size, their relationship with the surrounding urban fabric, their connection to the metropolitan network—both in terms of transportation and Green Infrastructure—and also in the diversity of their design.

4.1. Systemic Overview

• Although the location of the parks responds to certain criteria of spatial equity (efforts have been made to avoid concentrating the parks in just a few municipalities, instead seeking spaces for this use throughout the entire geography), their characteristics do make them quite different. The analysis of the parks sample shows that there is no correlation between their location (more central or more peripheral) and their size. Central parks (in denser urban areas) are not smaller than those on the urban edges: a phenomenon that can be explained by the lower demand from nearby populations in the latter, and because in many cases, there is a clear continuity between the park of limited dimension (technically in the limits of “Urban Land”) and the open forest or agricultural spaces (technically in “Non-Building Land”) [5].
• Regarding their contribution to Green Infrastructure, it is confirmed that in all cases, due to their size, the parks are valuable elements at an intermediate scale between the major green systems (river areas, agricultural parks, coastal mountain range, etc.) and urban greenery, which is often relegated to small public spaces (sometimes not very green) and tree-lined streets. This intermediate scale approach contrasts with other Mediterranean approaches, such as in Milan, where the focus seems to be placed on the development of peripherical green structures of a larger size that extend beyond the urban scale [31,36]. Nonetheless, the role of Metropolitan Parks changes depending on their position, either on built or unbuilt areas, and if they are in continuity with regional Green Infrastructures, as the eco-systemic services provided respond to those of inhabitants in close proximity or take on the role of providing important links between natural habitats [44]. To ensure these roles, it can be considered that improving their internal configuration is just as important as the series of coordinated actions that allow their efficient and practical interconnection with the surrounding open spaces of different sizes [43]. In fact, ecology is a key component of the park’s program: as the need to incorporate ecosystemic services linked to the needs of the citizens become imperative, the possibility to serve both local and metropolitan needs is an interesting by-product of this challenge, faced by cities such as Barcelona, which consider parks as part of a network of climate shelters. Ongoing efforts actively aim to incorporate ecological restoration strategies, the creation of evolving and resilient landscapes, specific installations for environmental education, and connectivity requirements that extend beyond the park’s boundaries, among other initiatives, also seen in cities such as Paris and Milan [34,35]. In this way, the activities within the park also trend towards catering to an “active community” that is more participatory and less reliant on structured programming [45,60].
• The view of the parks from their perimeter varies significantly between cases, although they commonly tend to be quite lacking in uniformity. This characteristic has historically influenced the placement of their entrances and will allow for a certain specialization in the distribution of uses within the park, as well as the appropriate placement of new functions in the future. A broader perspective highlights segments of the perimeter that connect with agricultural or forested areas, thereby extending the park’s ecological functions far beyond its boundaries, allowing a “Park of Parks” approach, as seen in Paris [42]. Conversely, several parks have “hard borders” where they border infrastructural elements such as the railway tracks or big road arteries, resulting in a kind of “non-relationship” along those sections and limiting possible continuities.
• In the balancing act between the functions hosted by parks and their degree of urbanization, a certain specialization of spaces stands out—the result of demands from various social groups and a strong commitment to public investment aimed at meeting citizens’ expectations. In any case, the desire to respond to social demands must be balanced with the ecological values of the parks themselves. This tension helps explain recent trends toward greater naturalization of these spaces and growing appreciation for newer design aspects, such as their role as climate refuges, a trend also observed also in other major European cities such as Paris and Brussels [34,61].

4.2. Design Strategies to Scale up Local Parks

Alongside the analytical characterization of the eight selected parks, their latent potential was investigated through a series of research-by-design studios. Led by faculty and senior students at the Barcelona School of Architecture (ETSAB), these design-based explorations produced a diverse set of inspiring proposals. As discussed in Section 2, working with the same sites across multiple scales-each iteration foregrounding different spatial values, constraints, and territorial dynamics-proved highly effective in uncovering latent design opportunities. This iterative, exploratory framework enables a nuanced assessment of which strategies perform best under varying urban conditions. Rather than applying a linear, object-focused methodology, the approach embraces the speculative, synthetic, and context-responsive nature of urban design as a discipline.

Efforts have been made to address each park’s aptitude for improving health and social interaction, its role in urban and peri-urban planning, its contribution to environmental and ecological balance, and its potential for leisure, recreation, and sport, highlighting their most common functions. The transformations to be proposed refer to both metropolitan and local scales, internal composition of the park, its relationships or externalities with its environment, and/or as open spaces, mobility infrastructures and buildings (public and/or private) are integrated up to different degrees within the change (see Figure 8).

• Promoting New Public Buildings and Increasing Attractiveness: A program capable of drawing publics from diverse parts of the city can act as a catalyzer for the park’s transformation, repurposing infra-utilized spaces, such as over-sized car parks and obsolete facilities present in parks like Fontsanta (Park Six) to avoid encroachment on permeable soil. A constellation of “metropolitan facilities” could connect several of these parks also through the services provided.
• Underlying or Intensifying Focal Points: Certain areas of the park can be highlighted as “focal points”, such as its entrances or gathering spaces. The aesthetic quality of an ornamental park that carries a notable amount of history behind it can be enhanced through a new understanding of eco-systemic values, as “climatic shelters” can renew the idea of a self-contained “Eden” as a reference for the whole city. Parks such as Torreblanca (5), Can Mercader (7) and Les Planes (8) could combine their historic past with these new perspectives.
• Scaling up Local Built Heritage: The integration of heritage evidences the interrelation between past and present as a boon for a park, reinforcing values of identity and place, as seen in Colònia Güell (3), a successful example of a park of metropolitan appeal through its appealing heritage value. Furthermore, the creation of post-industrial cultural landscapes is a chance to renew grey infrastructure within the park, as exemplified throughout Europe [31,62].
• Increasing “Porosity” of the Limits: Regarding the surrounding urban fabric and mobility infrastructure, low “porosity” limits are unable to connect separate neighborhoods such as in the case of Can Mercader (7). An opportunity is present considering potential “stretching” of certain key traces, the position of relevant public transportation facilities and the park’s relation with the diverse fabrics in its vicinity.
• Strengthening “Green Infrastructure”, taking into consideration the network recently designed in the drafting of the new Metropolitan Master Plan [2].
• Consolidating metropolitan ecological systems and promoting new ecosystem services both outside and within the park [63], by accounting for metrics such as the amount of permeable soil and the presence of water surfaces capable of sustaining small-scale ecosystems, among other recognized parameters [64]. Parks located on the western side of the Llobregat could reinforce the connection between forests and river ecosystems, which could be emulated in the eastern side by reducing the fragmentation present in more urban parks through the greening of adjacent grey infrastructure.

From a strategic perspective, the improvement of some of these aspects, and their selective combination in certain cases, offers interesting opportunities for enhancing the network of Metropolitan Parks. To their traditional role as local service elements that enhance their immediate surroundings and support outdoor activities for nearby residents is added a metropolitan role: as true nodes within a polycentric system and as key components of a Green Infrastructure that will form the backbone of the 21st-century metropolis.

5. Conclusions

Through the analysis of a selection of parks within the Barcelona metropolitan area, this research seeks to provide an innovative perspective on the role of Metropolitan Parks, not only as key elements within the green infrastructure network but also as nodes of centrality that can strengthen the polycentric structure of metropolitan region.

The research has highlighted the importance of a comprehensive understanding of the various dimensions of the parks, considering different scales of analysis and taking into account factors such as metropolitan positioning and accessibility, the degree of permeability in their boundaries, their ecological components and contribution to green infrastructure, and finally, their internal landscape composition. Taken together, these factors determine the extent to which parks can play a prominent role in fostering social cohesion and becoming reference spaces for citizens.

While this research is inspired by the particular polycentric structure of the Barcelona metropolitan area, it is considered that the analytical methodology developed can also be extrapolated to many other cities. Although the approach is valid for the individual study of parks regardless of their size, the methodology is particularly relevant when used for a comparative analysis of elements that share similarities and differences. This allows for a better understanding of the characteristics, deficiencies, and potentials of each park.

Further research could be developed by expanding the methodological tools, adding to the mapping and parameterization work a more social approach focused on the actual use of these spaces. This could be carried out using instruments of the social sciences, such as interviews, among others.

Overall, the research contributes to the broader debate on how the necessary presence of greenery in cities can be effectively combined with other essential functions, such as centrality, by testing, through urban design, the most appropriate design formulas for making cities more sustainable and liveable.