4. Results and Discussion
The first part of this paper details the process of the archaeological mapping. Once the survey was completed, a total of 1665 archaeological sites were identified, spanning from the Late Bronze Age to the Late Roman occupation (
Figure 6, above). Their distribution underscores the island’s archaeological density and diversity, covering all four regional units: Chania (western Crete) with 347 sites; Rethymno and Heraklion (central Crete) with 119 and 663 sites, respectively; and Lasithi (eastern Crete) with 535 documented sites. This regional breakdown enabled a detailed and comparable analysis of each area, facilitating the detection of recurrent patterns and occupation dynamics across the island.
In addition, the systematic classification applied to each record—supported by a validation scale—served two main purposes. First, it established a rigorous framework of systematisation, ensuring consistency and normalisation in the treatment of sources and data. More importantly, it improved the overall precision of site location and enabled a critical appraisal of the confidence associated with each dataset. This was crucial, since locational accuracy directly affects the contextualisation of archaeological evidence and, consequently, the interpretation of results (
Figure 6, below).
Figure 6.
(Above) Map of Crete illustrating the locations of ancient sites from the Late Bronze Age to the Late Roman period documented in the study. (Below) Examples of archaeological sites categorised according to the level of source accuracy and validation.
Figure 6.
(Above) Map of Crete illustrating the locations of ancient sites from the Late Bronze Age to the Late Roman period documented in the study. (Below) Examples of archaeological sites categorised according to the level of source accuracy and validation.
The second part of this paper presents, in detail, the procedures for mobility and network reconstruction, which are organised in two distinct phases: (i) an initial (re)constructive phase and (ii) a subsequent analytical phase. Although the workflow comprises conceptually discrete steps, it was implemented using Python 2.7 integrated with ArcGIS (v.10.5). This approach enabled the optimisation of data management and the automation of the entire workflow.
First, the working environment was established and configured based on the delimitation of the study area—i.e., the entire island of Crete—using a Digital Elevation Model (EU-DEM, Copernicus) with a spatial resolution of 25 m and the hydrographic network encompassing the region. Regarding the latter, extensive work was carried out using hydrological tools and remote sensing data integrated within the GIS platform. The objective of this approach was to model these systems and produce an accurate representation of areas with the highest potential for flow accumulation and flood risk, taking into account the characteristic seasonality of Mediterranean environments (
Figure 7).
To generate an Accumulated Cost Surface (ACS) that explicitly incorporates movement friction, we first quantified the influence of the main environmental drivers on regional mobility, which are the topography and the hydrographic network. Slope values were calculated as percentages instead of degrees, recognising that steeper gradients impose higher travel costs. Concurrently, the hydrographic network was assigned a specific resistance by buffering the channels by 100 m on either side (Euclidean distance) and applying a graded cost that rose to a maximum of 15% through a conditional expression (
Figure 8). The 100 m buffer represents an average riparian zone where movement may be broken by unstable banks or seasonal flooding. As the model is based entirely on the DEM, it already incorporates steep slopes, fault scarps and fractured terrain.
The resulting layer was then transformed with Naismith’s rule to approximate human walking speed. On level ground, an adult can cover ~5 km h−1, or 12 min km−1, but for every 10 m of ascent (≈1% gradient), an extra minute is added—an 8.33% increase in cost. Thus, at a 12% gradient, the cost effectively doubles relative to flat terrain. Operationally, the friction factor X was computed with X = 0.0833 × P + 1, where P is the slope (%) and X is the resulting cost, yielding a more realistic portrayal of how environmental conditions shaped human mobility.
Once the final cost surface layer or friction map (ACS) was generated, a grid of points was placed within an orthogonal mesh, and 5 km spacing was chosen as an optimal balance between spatial resolution and computational manageability. This resolution provides a sufficient sample size to produce coherent and spatially representative results while remaining within the processing capabilities of standard GIS software. In total, 331 simulated points were established to represent destination sites (
Figure 9). By deliberately excluding previously documented archaeological sites, the objective was to minimize potential biases in the model, thereby enabling an exploratory approach in which patterns and areas of interest could emerge organically from the model itself, rather than being influenced by known site locations. With both the point grid and the friction map integrated, the sequence of operations associated with the FMN methodology was then executed.
During analysis, the process was repeated for each of the destination points, generating multiple raster files per iteration—namely, cost distance, flow direction and flow accumulation. In this case study, with 301 destination points, a total of 903 raster layers were produced (3 per point). This has important logistical implications in terms of both processing time and storage capacity. Consequently, it is essential that archaeologists intending to apply this type of approach should be aware of the associated computational demands.
Finally, to generate the integrated network, the average of all the flow accumulation raster layers produced for each destination point was calculated. This resulted in a single raster file that visualises the network of potential routes or corridors structuring mobility across the island (
Figure 10). In this raster layer, each cell contains a value representing the accumulated cost of travelling from any point within the study area to each of the destination points. By visualizing these potential routes, it becomes possible to identify the key corridors likely to have connected different regions, highlighting routes and areas characterised by the lowest cost and, consequently, the highest accessibility. This approach has not only facilitated the interpretation of mobility across Crete but also provides a foundational framework for reconstructing patterns and dynamics of interaction, communication and exchange throughout its landscapes.
As shown in
Figure 10, the application of the FMN method produces a large number of routes due to the nature of this type of analysis. This high volume of data can complicate the interpretation of results. Therefore, it is necessary to conduct further processing to retain only the most significant routes—those that represent the greatest potential for mobility. To achieve this, the accumulation values were reclassified based on specific thresholds in the raster data to derive a vector-based network. In this regard, Llobera, Fábrega-Álvarez, and Parcero-Oubiña [
22] emphasize that there is no strict rule for determining the appropriate threshold, as different thresholds reveal different hierarchical levels within the resulting network structures. Nonetheless, they propose a guideline based on factors such as the size of the study area, the pixel resolution and the desired density of the network for analysis.
In this study, to ensure methodological consistency with previous applications, we adopted parameters established in earlier works—particularly those of Sylviane Déderix [
28,
29]. Déderix applied this methodology to the Messara Plain in south-central Crete during the Early Bronze Age, using a reclassification based on 1/4 standard deviation. The same criterion was adopted here, resulting in the retention of only the primary routes or corridors with the highest potential for mobility (
Figure 11). Additionally, to explore the strength of connections in terms of intensity, the values were further configured to emphasize corridors with the highest accumulation levels—that is, areas with the greatest potential circulation (
Figure 12).
Overall, the results indicate greater connectivity along coastal areas compared to inland regions. This pattern is generally consistent, with a few notable exceptions, such as the south-central coast, where the Asterousia Mountains serve as a natural barrier between the Libyan Sea and the island’s interior. In this case, mobility corridors are redirected through adjacent areas, particularly the Messara Plain, which functions as a natural pass and emerges as a strategic transit point linking different parts of the island. The routes or corridors with the highest accumulation values—those with the greatest potential for circulation—converge along two main trajectories. The first follows a west–east axis along the northern coast, beginning in the Chania region and connecting key locations via natural passes such as the Selinari Gorge. This corridor links the north-central region with Agios Nikólaos and continues towards the Bay of Mirabello, where it branches out towards the easternmost parts of the island. The second main corridor follows a similar direction but diverges southward from Apokóronas, connecting with the Messara Plain. From there, it continues eastward along the southern coast towards Ierapetra and ultimately links with the easternmost regions of the island.
In terms of accessibility, the areas connected by these primary corridors exhibit a clear advantage over other regions. This is strongly evidenced by the strategic placement of key centres of occupation and human activity during the periods under consideration such as Kydonia, Knossos, Phaistos, Kommos, Gortyna, Mochlos or Palaikastro, which are all situated in close proximity to these main transit routes. This spatial advantage is reflected in the socioeconomic dynamics of these sites, where accessibility likely played a central role in facilitating the growth and development of local communities. Consequently, proximity to these routes appears to be directly correlated with the socioeconomic flourishing of the aforementioned areas. These results suggest that accessibility was a fundamental driver of economic growth and social complexity, enabling sustained flows of communication and exchange across the island.
These results offer clear responses to several of the research questions posed, providing a detailed understanding of historical patterns of mobility and settlement in Crete. First, the most probable corridors for reaching specific destinations are shaped by accessibility, which is notably higher in coastal zones and in the valleys that connect the northern regions with the central southern part of the island. Moreover, when comparing different areas, it becomes evident that the principal centres of human occupation and activity during the periods under study are strategically situated at key points along routes with the highest potential for movement. This spatial alignment underscores the importance of accessibility in shaping patterns of human settlement and interaction.
Thus, accessibility not only facilitated mobility between different areas, but may also have significantly influenced the location and distribution of settlements along these communication corridors. Indeed, the choice of where to establish major centres such as Knossos, Phaistos or Gortyna was likely not accidental but shaped by their strategic placement along natural transit routes. These corridors provided reliable lines of movement, resources and communication, making them decisive factors in the foundation and longevity of urban centres. Of course, accessibility was only one among several considerations—religious traditions, political authority and symbolic landscapes also played important roles—but it must be regarded as one of the principal determinants shaping settlement planning and civic organization. Crucially, accessibility also extended to maritime routes, ensuring connectivity not only within Crete but also across the wider Aegean and Eastern Mediterranean. In this respect, settlement patterns reveal both continuity with earlier Bronze Age traditions of seaborne interaction and moments of rupture, when shifting political, economic or cultural dynamics redefined how communities engaged with the sea. Furthermore, the mobility routes identified largely correspond to natural pathways that Cretan societies likely utilized to connect various parts of the island, thereby forming a historical network of routes that enabled sustained interaction among communities.
Although these results provide a comprehensive framework for understanding long-term settlement and interaction patterns across Crete, certain challenges persist. Future research could expand the scope by incorporating additional data and considering a broader range of variables to further refine the models. Additionally, the quality of the results is inherently tied to the resolution of the Digital Elevation Model (DEM), the density of destination points and the cost function employed. Moreover, while FMN routes provide a plausible reconstruction of ancient mobility on Crete, it is important to acknowledge that these models are hypothetical constructs rather than direct archaeological evidence. They do not fully account for potential changes in route utility over time or the influence of specific sociopolitical factors. Although the consistency between historically known and modelled routes is noteworthy, the results should be cross validated with field evidence wherever possible. Additionally, comparative studies with other Mediterranean regions could offer valuable context, situating the mobility patterns observed in Crete within a broader regional framework.
However, as emphasised throughout this study, the analysis has not been limited to the examination of sites and routes alone. In alignment with the theoretical framework underpinning this research, sites of human occupation and activity—along with the identified historical routes, roads and mobility corridors—are conceived as components of an interconnected network. This conceptualisation enables the integration of these elements into flexible trajectories within structures that can be navigated in any direction, not merely along the shortest or most efficient paths. Adopting a network-based perspective fundamentally transforms the analysis of these processes. While cost or friction surfaces consider the entirety of passable space, a network represents a set of structured elements that articulate flows of communication and exchange across multiple levels and scales. Although this approach may appear to entail certain theoretical limitations—such as the exclusion of interactions occurring outside the network—it also provides significant analytical advantages, as will be discussed in the following paragraphs.
The first consisted of a study of the network as a whole, focusing on the role played by each section, that is to say, the specific function performed by each route within the general dynamics of the network. To do this, we started from the flow accumulation values obtained, which allowed us to infer the potential circulation throughout the network, in combination with the Spatial Design Network Analysis (sDNA) application package. These types of tools allowed us to conceptualise and evaluate the routes as entities within the spatial network, facilitating the analysis of key metrics such as the degree of centrality, intermediation and proximity.
Degree centrality was employed to measure overall connectivity within a defined radius of the network at distinct spatial scales, in this case, 20 km and 50 km. This metric calculates the number of connections at each intersection or junction within the specified radius, weighting each one according to the sum of the accumulation values (i.e., traffic intensity). Betweenness centrality was particularly valuable for identifying key routes within the network, those functioning as critical axes of connectivity. This metric evaluates the frequency with which a route segment is used as an intermediate step in connecting different parts of the network, thereby highlighting the most frequently traversed corridors. These strategic routes are often vital to the overall stability and functionality of the network, as their disruption could fragment the flow of communication and exchange. Finally, closeness centrality offered a complementary perspective by emphasizing the accessibility of each route within the network. This metric measures the proximity of each segment relative to all others, thus identifying routes that facilitate fast and direct access across different areas (
Figure 13,
Figure 14 and
Figure 15).
This exploratory analysis has enabled a comprehensive evaluation of the historical mobility networks in Crete, revealing both the overall connectivity of the network and the presence of strategic corridors, those characterized by high betweenness centrality and routes that facilitate direct access, as indicated by high closeness centrality. These metrics, calculated using values that reflect potential circulation, have been instrumental in deepening our understanding of how these networks shaped the socio-spatial dynamics and territorial organization of the island, as well as the historical mobility patterns that emerged and evolved over time.
The results highlight the pivotal roles played by specific routes and nodes in shaping patterns of mobility, communication and exchange. Notably, central Crete encompasses the majority of the strategic land corridors and accessible pathways identified through centrality measures, offering compelling evidence of a well-integrated system designed to support the island’s socioeconomic and sociocultural functions. The fertile plains of central Crete, combined with their proximity to key urban centres, positioned this region as a natural nexus for trade and communication, effectively connecting the eastern and western parts of the island. However, it is essential to incorporate maritime connections (cabotage) into the analytical framework. These maritime networks facilitated the movement of goods and people between coastal settlements, effectively bridging otherwise isolated regions and enhancing the overall connectivity of the island. This analysis also underscores the resilience and adaptability of these historical networks. The relationship between highly connected nodes and strategic routes reveals a system optimised for both stability and efficiency. This aligns with the prominence of significant multi-period urban centres such as Knossos, Phaistos and later Gortyna and Ierapytna, which emerged within these interconnected areas. These centres functioned as hubs for governance, resource distribution and cultural exchange, leveraging strategic land corridors to maintain their influence over both nearby and distant settlements. From a cultural point of view, while all the important Cretan centres did not coexist throughout antiquity, there are clearly several important avenues for further investigation in future studies. One such example is the relationship between the strategic land corridors computed in the present research and the main Roman and Late Roman networks as depicted in the Tabula Peutingeriana. The main city centres shown on the Roman map are mostly located along the principal land corridors identified in this study. This will form the next step in the authors’ research, where environmental factors will be analysed alongside cultural aspects in specific periods as part of a Research Programme [
38,
39].
5. Conclusions
Building on this methodology, the mapping process offered a long-term perspective on settlement patterns, while FMN modelling identified the natural corridors that likely channelled past movement across the ancient Cretan landscape. By integrating different variables, the models underscored the interplay among topography, hydrography and other factors in shaping patterns of settlement and interaction. The raster outputs depicted the spatial configuration of probable pathways, revealing high-potential routes that correspond with documented traditional tracks and pointing to new areas that warrant further investigation.
In this way, this study identified several primary mobility corridors with varying levels of accessibility. As outlined earlier, two major mobility axes were detected: (i) The first follows an east–west trajectory along the northern coastline, linking key areas including Chania, Heraklion, Sissi, Agios Nikolaos and Mirabello Bay, and extending to the easternmost regions of Sitia. (ii) The second connects the northwestern part of the island with the Messara Plain and extends along the southern coast to Ierapetra, and from there reaches the eastern zones. Overall, coastal pathways offered relatively lower friction and thus facilitated exchange, trade and communication. The exception is the south-central region, where the Asterousia Mountains act as a natural barrier. In this area, mobility was concentrated through the Messara plain, a strategic zone connecting the interior and coastal regions, where natural corridors such as valleys, plains and mountain passes served as critical conduits of past movements.
From a historical perspective, these identified mobility axes underline the importance of accessibility in shaping the distribution and development of sites on ancient Crete. Major urban centres, such as Kydonia, Knossos, Malia, Phaistos, Gortyna, Ierapytna or Gournia, are strategically located along these primary mobility corridors. This correlation suggests that proximity to accessible routes was a decisive factor in the growth of these communities. The enhanced connectivity facilitated by these corridors likely supported economic activities, social interaction and cultural exchanges, contributing to the sociopolitical complexity observed in these areas during the analysed periods. The emphasis on accessibility also provides insights into the spatial organisation of settlements, suggesting that historical populations strategically utilised natural corridors to optimise communication and resource distribution. Thus, the observed patterns of mobility indicate that the rugged landscape of Crete served not only as a constraint but also as an enabler of connectivity and interaction, thereby shaping the island’s sociocultural and socioeconomic trajectories.
Beyond demonstrating patterns of accessibility, the reconstructed corridors may indicate how mobility, and in essence, proximity and access to major routes, shaped the social and cultural landscapes of ancient Crete. The alignment of these routes with major centres suggests that mobility networks did more than facilitate commerce and economic exchange; they also structured intercommunity relationships. In several instances, terrestrial corridors intersected with coastal nodes, creating points where land and sea routes converged and reinforcing the dual importance of overland and maritime communication. These intersections likely served as hubs for the redistribution of goods, ideas and people, embedding mobility into nearly every aspect of society. It is important to note, however, that most major Cretan centres, with some significant exceptions such as Roman Hierapytna, were situated inland at a considerable distance from the coast. Knossos, for example, which controlled more than one harbour in the present-day Heraklion area, lies about 5 km from the shoreline. Overall, the reconstructed routes should not be viewed simply as technical models of past movement but as integral elements in the negotiation of power, identity and interaction within the Cretan world.
Consequently, settlement strategies on Crete adapted not only to shifts in resource availability and ecological conditions but also to human capabilities, illustrating the resilience of its societies. Its enduring role as a socioecological ‘historical palimpsest’—i.e., a layered record of coevolutionary interactions between human and non-human forces, with each period leaving its imprint on the landscape—highlights the intricate interplay shaping Crete’s natural and social trajectories. Understanding these landscapes as both a physical and dynamic social record of human–environment interactions provides a robust foundation for interpreting Crete’s historical and ecological narratives.
At the second level, the analytical approach centred on the overall network structure emphasised the specific roles of individual routes and nodes within the network’s dynamics. Utilising flow accumulation values and the Spatial Design Network Analysis (sDNA) toolkit, the analysis quantified topological key network metrics such as degree centrality, closeness, and betweenness to identify the multifaceted roles of nodes (e.g., key connection points) and edges (e.g., mobility corridors) within these networks. These metrics allowed for a nuanced understanding of the connectivity, strategic importance and accessibility of routes at different spatial scales. (i) Degree centrality: This metric highlighted the overall connectivity within specific radii (20 and 50 km), identifying intersections or crossings with the highest concentration of connections. Weighted by flow intensity, degree centrality underscored how certain routes facilitated high levels of circulation, making them essential for maintaining the network’s coherence. (ii) Betweenness centrality: The analysis of betweenness centrality was pivotal in identifying key corridors within the network. These routes, frequently used as intermediaries connecting different parts of the network, emerged as critical to its stability. Their disruption could fragment communication and exchange, illustrating their centrality in maintaining the network’s integrity. (iii) Closeness centrality: By focusing on accessibility, this metric provided insights into routes that enabled rapid and direct mobility across the network. The metrics underscored the importance of certain pathways in optimising connectivity and fostering direct interactions between different zones.
Collectively, the results reveal a comprehensive picture of the historical networks in Crete, delineating the strategic corridors and urban centres that optimised both local and regional connectivity. These elements likely had profound implications for the island’s socio-spatial dynamics, influencing patterns of interaction, communication and territorial development over time. Thus, the application of this approach to the study of ancient Cretan connections has yielded significant insights into the spatial and relational dynamics of historical settlements and their connective infrastructure. Therefore, this analysis has revealed a nuanced ‘big picture’ of how distinct elements structured and influenced patterns of communication, exchange and social interaction within the ancient Cretan landscapes.