Managing Sustainable Urban Tourism Development: The Case of Ljubljana

The interest in sustainable urban development and sustainable tourism development is growing. Yet, according to our knowledge, only a limited number of studies combining those two areas exist, and the holistic model for sustainable urban tourism development has not been introduced. Our study aims to integrate sustainable urban development scientific area with sustainable tourism development scientific area and to integrate and advance the existing models for sustainable urban tourism development. As a method for analyzing the results of 322 interviews, we used content analysis. Based on the analyzed data, the conceptual sustainable urban tourism model is proposed and applied to the case of Ljubljana. The results show that Ljubljana needs more emphasis on sustainable urban tourism development by considering different dimensions of sustainability, stakeholders, as well as types of tourism. Specifically, respondents took into consideration social, environmental, as well as economic sustainability. The most often mentioned stakeholders were local communities and companies; meanwhile, according to their opinion, Ljubljana has the greatest potential in cultural, green, and sports tourism. Finally, the study integrates sustainable urban development and sustainable tourism development scientific areas by providing a conceptual model and taking into consideration the need for proper management, ranging from planning to education and policy-making.


Introduction
Global warming, climate change, pollution, emissions, food shortages, depletion of natural resources, desertification, and other threats [1] are some of the key challenges of contemporary societies. In the past 70 years, tourism has extensively grown, due to technological innovations in traveling and the transportation industry, economic growth, and rise in disposable income [2]. The focus of sustainable tourism is on the natural environment, rural setting, and protected land, even though the majority of the people in the world live in urban areas and cities are most traveled to [3]. Sustainable urban tourism development (SUTD) is a crucial subject due to the trend of urbanization, the rise in the world population's financial and technological ability to experience life in other parts of the world. Ljubljana was among the capitals that invested a great deal into an integrated marketing mix to attract tourists; however, now that it is a "hot" and popular tourist attraction, concern also arises in the government of the city as to how to sustainably manage urban tourism development. However, also some other global cities are already facing the negative effects of massive tourism (e.g., Venice, Dubrovnik, Barcelona, etc.), and cities need to develop in line with the sustainable development goals (SDG). The United Nations presented Sustainable Development Goals (SDG) [4], which represent a global strategy for achieving a resilient future for all stakeholders. The 11th SDG deals with a specific urban goal of making cities and human settlements inclusive, safe, resilient, and sustainable, while

Sustainable Urban Development
The term sustainability was first used as Nachhaltigkeit (the German word for sustainability) in 1713 [17,18], and it meant never using more than what the forest yields in new growth [19]. The European Commission released in 1987 Our Common Future report. At the core of the report was the principle of "sustainable development," which is also gaining an important role in the educational agenda [20]. The EU Commission's acceptance of sustainable development as a guideline offered credibility to an old concept others worked in the past [8]. The EU Commission named sustainable development as "meeting the needs of the present without compromising the ability of future generations to meet their own needs" [8,9]. Linear and unidimensional thinking processes are not suitable when defining the future sustainable plan, as decision-makers need to take into consideration different stakeholders as well as understand sustainability through networks and organic alliances [21].
Management for achieving sustainable, low-carbon adaptive reuse needs to be designed more holistically, integrating economic, social, environmental, urban, and political policies [22]. City sustainability goes beyond the quality of life, as cities need to find the balance between being part of a competitive global city community and meeting the needs of the daily requirements of their inhabitants [23]. A sustainable city responds to social, environmental, political, cultural objectives, economic and physical requirements [23].
A total of 1410 articles on sustainable urban development have been published [20]. The sustainable urban development construct has been gaining in popularity among researchers since 2011 [24].
In addition, the sustainable urban development construct was most often studied within the environmental sciences ecology, followed by urban studies, science technology on other topics, engineering, and public administration, according to the Web of Science Core Citation results [24].
Strategical environmental assessment [25] measures the environmental impact of plans, programs, and policies. Cultural heritage, energy consumption, carbon emissions, and waste management are part of urban sustainability [26]. There are four models of the dynamics among cities and their environmental hinterlands, such as redesigning the city, self-reliance, external dependency, and equitable balance [27]. Adaptive reuse of buildings is a mode of sustainable urban regeneration, as it extends the building's functionality and avoids waste, encourages reuse of energy, and also provides social and economic benefits to the community [22]. Also, artists, as a subgroup, make substantial, valuable contributions to the functioning of cities [28].
Effective urban development tendencies are influenced by joint actions of state authority and the city [29]. People within Central and Eastern Europe are more influenced by the pride and self-esteem encouragement connected with empowerment and the perceptions of community cohesion than the economic promises of tourism [30]. Favorable starting conditions for green mobility are successful financial and institutional implementation strategies [31]. Better marketing and closer cooperation among transport providers and planners with tourism attractions and accommodation providers were identified [31]. Positive festival impacts are influenced by emotional solidarity and community attachment [32].

Sustainable Tourism
Sustainable tourism is a way of tourism development or tourist activity, complementing the environment, ensuring long-term protection of resources, as well as ensuring social and economical acceptance and fairness [12]. The definition of tourism and its several types needs to be focused to enable standards and meet the interests of the tourists [33]. Sustainable tourism is difficult to define and implement [34], as it emphasizes the activities of local stakeholders [35]. Research on sustainable tourism gained momentum in 2008 and has been a popular research construct since 2015 [36]. Among a range of research areas, the sustainable tourism construct is by far the most studied within social sciences than other topic fields, followed by environmental sciences ecology, science technology, other topics, and business economics [36].
Sustainable tourism research demonstrates the use of an appropriate scientific methodology, such as is the interpretive paradigm in the highest degree [12]. A deficiency of research on circular tourism [37] was found.
Urban tourism [38] was researched in the 1960s mainly by geographers and gained renewed attention in the 1990s [39]. Urban tourism has the potential to drive economic growth, as well as promote inclusive development to the region [40]. The following themes are emphasized within urban tourism research: sustainability, planning, management, impacts, cultural agendas, visitor perception and satisfaction, urban regeneration, models, typologies of tourist cities, city case studies, social theory, transport and infrastructure, marketing, and place imagery [41]. Spatial distribution of users, i.e., their origin neighborhoods, affects satisfaction with the services, demonstrating social inequity patterns [42]. There is a discrepancy among the views of industry and academia in terms of who sets priorities for urban tourism. Industry places emphasis on issues that serve their direct commercial interests, rather than reflecting the broader interests of other stakeholders, such as the environment [43].
In multifunctional entities, tourists' motivation for going can differ greatly. The construct of sustainable tourism has multiple aspects and different researchers emphasize different facets. Among others, the latest research is focused on overtourism [44], by refocusing on the well-known problem of managing negative tourism impacts on core challenges [45] between the quality of life for residents and the city development to have a positive impact on the tourism industry, sharing economy as a new business model [46], existing difficulties in defining solutions to activation and diffusion of sustainable urban tourism practices [2], or preparation of destinations to be smart in line with co-participative tourism [47].
Despite the undeniable importance of the sustainable approach to tourism, a lack of investment in sustainable practice of tourism is identified [48]. Nevertheless, also the size of the establishment affects commitment to sustainable development as large-and medium-sized hotels show higher commitment [49]. However, tourism sector stakeholders are aware of the vital role sustainability has [48,50]. An assessment system for sustainable tourism was developed facilitating the ranking of tourism regions according to their sustainability degree [50]. In addition, it was also researched how sustainable tourism can be enhanced by mobile connectivity through new space-time practices to create social groups who are interested in sharing [51]. The importance of the decision-making process in the sustainable management of tourism development and utilization of the typology of community decision-making influence factors that need to be considered for effective sustainable tourism implementation [52]. Sustainable tourism was bridged with psychological factors, focusing on emotions [53]. Studies that measure visitors' behaviors longer than a year post-trip are missing [54]. Conservation psychology and environmental education claim that extended and repeated experiences are key for sustaining the initial motivation to develop new long-term behaviors [54].
SUTD has different activities and services than other forms of tourism [2]. SUTD demands a complex system of integrated elements, such as attractions, accommodation, transportation, retail, travel trade, food, and beverages [55]. Part of the city tourism industry needs to be a destination management organization, responsible for development and planning, in order to enable SUTD [13]. Urban and environmental problems have roots in ecology and urban contexts, and therefore, city governors need to plan, design, and manage urban settlements in a way that allows inhabitants to preserve their quality of life [56]. Annual budgets are needed to perform different activities in urban areas to protect the environment and tourism management, ranging from employing professionals to do maintenance and cleaning, surveillance, visitor assistance, and information, limitation of vehicle access, as well as investments in infrastructure and equipment for public use and conservation of local wealth and landmarks [57]. Recent study shows that city governors should also invest in the Big Data and eliminate common errors in big data databases (missing data, duplicate entries, errors generated by the data custodians and others), which can then help cities to become smart, utilize resources more efficiently and improve inhabitants' quality of life [58]. Quality of life affects urban growth and competitiveness [59]. Culture is an essential element of urban transformation due to its role in promoting consumption and territorial marking in the context of global tourism and economic flows [60]. The right to the city influences urban policies [61] and indigenous culture should not be lost due to massive tourism [62], as it is an important element of the social capital of an urban destination [63]. Massive tourism also produces pollution [64] that affects the quality of life and tourist carrying capacity needs to be included in planning for sustainable tourism [65]. Cities should be inclusive, to avoid urban poverty and inequality [66]. When studying urban ecosystems, social and natural sciences need to be connected. Ecology needs to be integrated with urban planning and design to address urban resilience capacity [67].

Conceptual Model Development
The conceptual model is developed, as presented in Figure 1. In the literature, partial views are existing and we have advanced the argumentation further. Participative management perspective towards sustainable urban tourism development is needed as a lack of triple bottom-line appreciation among tourism industry stakeholders was identified [13]. We formed the conceptual model on the basis of the existing literature review. The conceptual model combines the proposed layers, as they have been identified as missing in the existing literature and supported by research findings. Each layer presents a different perspective that needs to be taken into consideration when developing sustainable urban tourism. It combines different perspectives on sustainable urban tourism development by combining different layers, namely: dimensions of sustainability (environmental, economic, and social) [68]; different stakeholders: individuals, companies, local community, and country/regional level; relevant types of tourism that can be developed in selected urban environments based on resources available; as, for example, family, green, shopping, gastro, cultural, business/industrial, sports, party, congress, educational, political, medical, nautical, intergenerational, wellness, or religious.
All those levels, namely types of tourism, stakeholders, and sustainability dimensions, should be combined in all available combinations and put under consideration when deciding on future urban sustainable tourism development. Every type of tourism has a specific segment of tourist and tourism types also share some key stakeholders, such as regional, local community, companies, and context matters, e.g., if green tourism is based on the value of environmental sustainability, this means that city governors need to invest more managerial effort into also developing economic and social sustainability. The selected areas should be appropriately managed [69]; namely, planned, organized, led, as well as controlled. Triple bottom line, including environmental, social, and economic indicators, are recommended within SUTD but rarely fully implemented [13], which is why we added a layer of management process in our model to emphasize the connection between sustainability dimensions and management functions. The participative model of SUTD is based on sustainability networks, which represent the interactions and management of different stakeholders' interests, goals, and powers [2,13].

Method
The research question of this study is "How to strategically manage sustainable urban tourism development?" In order to be able to answer our research question and apply the proposed conceptual model, we selected the qualitative approach, which is advised to research an underdeveloped field to gain an in-depth understanding of the phenomena under study. Specifically, the case study [70][71][72] of Ljubljana, the capital of Slovenia, is applied. When studying sustainability, with the case study approach, research is frequently focused on analyzing an example [12]. In addition, the studies that apply qualitative methods prevail [12].
The chosen approach to researching sustainable urban tourism development is content analysis and quantification of qualitative data, to really understand how the informants (tourists and inhabitants) perceive Ljubljana and its potential for further sustainable urban tourism development. In order to grasp a deeper understanding, their narratives were also collected and analyzed. We quantified the qualitative data and also provided in vivo proof citations. Informants were asked how they view the development of tourism in the capital of Slovenia by providing an explanation for their choices. The Stanford social innovation questionnaire was applied by the research team of 10, asking tourists, visitors, and inhabitants of Ljubljana the following questions regarding the researched topic of how to design tourism development with the support of visitors, tourists, and inhabitants who share it: Narratives are formed in the sociocultural setting in which the narrator functions; that is why the purpose of the narrative analysis is to understand both the narrative as well as the sociocultural context [21]. Joint content analysis of the answers by the authors was chosen as the most suitable method for analyzing the responses, aiming to find the preferred sustainable urban tourism development. The content analysis aims to define concepts and theoretical formulations and is, as

Method
The research question of this study is "How to strategically manage sustainable urban tourism development?" In order to be able to answer our research question and apply the proposed conceptual model, we selected the qualitative approach, which is advised to research an underdeveloped field to gain an in-depth understanding of the phenomena under study. Specifically, the case study [70][71][72] of Ljubljana, the capital of Slovenia, is applied. When studying sustainability, with the case study approach, research is frequently focused on analyzing an example [12]. In addition, the studies that apply qualitative methods prevail [12].
The chosen approach to researching sustainable urban tourism development is content analysis and quantification of qualitative data, to really understand how the informants (tourists and inhabitants) perceive Ljubljana and its potential for further sustainable urban tourism development. In order to grasp a deeper understanding, their narratives were also collected and analyzed. We quantified the qualitative data and also provided in vivo proof citations. Informants were asked how they view the development of tourism in the capital of Slovenia by providing an explanation for their choices. The Stanford social innovation questionnaire was applied by the research team of 10, asking tourists, visitors, and inhabitants of Ljubljana the following questions regarding the researched topic of how to design tourism development with the support of visitors, tourists, and inhabitants who share it: Narratives are formed in the sociocultural setting in which the narrator functions; that is why the purpose of the narrative analysis is to understand both the narrative as well as the sociocultural context [21]. Joint content analysis of the answers by the authors was chosen as the most suitable method for analyzing the responses, aiming to find the preferred sustainable urban tourism development.
The content analysis aims to define concepts and theoretical formulations and is, as such, an element of the interpretation [73]. In total, 322 tourists and inhabitants of Ljubljana as informants (thereof 44.72% males) were interviewed in the Ljubljana city area, who gave answers to an open-ended social innovation questionnaire. Informants' perceptions of Ljubljana as sustainable urban tourism destination development were analyzed with the descriptive method, which offers a rich presentation comprehension of sustainable urban tourism development. Proof citations [74] of the phenomenon demonstrate the depth of their thinking. We have structured our analysis according to gender, habitation, age, and three content themes emerging from the data. Content themes were the following: (a) dimensions of sustainability [17], namely, what is the main focus of the participant's perceived sustainable tourism needs in terms of sustainability conceptualization, that is, economic, social, and/or environmental; (b) researchers identified key stakeholders responsible for sustainable tourism implementation in the capital, that is, individual, company, local, and country/regional level; and, (c) we have identified different types of tourism which have been mentioned by the informants as desired types of sustainable urban tourism.

Context of the Conceptual Model Application: The Case of Ljubljana
Ljubljana has made the Global TOP 100 Sustainable Destinations list for the fifth time in 2019, maintaining its position as one of the most sustainable destinations, [75] and held the title of European Green Capital 2016. It was chosen as a case study with the reason to advance Ljubljana tourism services and products management, established by previous successful accomplishments in the field of sustainable tourism, recognized by international experts, awards, and prizes. Management, digitalization, and smart solutions integration in the field of managing sustainable tourism in the city was elaborated as a challenge by the vice mayor of Ljubljana, Mr. Crnek [76]. The study was conducted with the aim to discover the potential for further advancement of SUTD. Ljubljana has in recent years developed into an urban tourism destination, and the city is changing considerably, and therefore, Ljubljana is a typical example. In order to preserve the city, it should encourage sustainable tourism development. How to do it-we asked respondents.
The capital of Slovenia, Ljubljana, is the administrative, cultural, political, and economic center of Slovenia and has 280,000 inhabitants. Ljubljana has been part of the Green Scheme of Slovenian Tourism since 2015 [77]. Three-quarters of the entire territory of Ljubljana are green areas, including contiguous aquatic, forest, and agricultural fields [78]. Nevertheless, Ljubljana has a rich historical heritage, ranging back to the Roman settlement Emona, and Medieval times (which are still evident), and it is also very close to the Alps, Mediterranean Sea, as well as other important sightseeing destinations, such as Postojna cave, Bled, Venice, Milan, Vienna, and Salzburg, and therefore, it is developing its tourism potential and it is vital for stakeholders that this development path is sustainable.

The Case of Ljubljana-Data Analysis
As presented in Table 1, the sample consisted of 322 informants, thereof 144 (44.72%) males. In total, 146 (45.34%) respondents had Ljubljana residency. According to the analysis, economic sustainability was identified in 27.64%, social in 86.02%, and environmental in 60.87% of total responses.  Table 2 presents the results regarding the impact on different stakeholders. The majority of informants, namely, 95.03%, mentioned impact on local community, followed by impact on companies (66.46%), country/regional level (12.11%), and only 2.48% targeted specific individual. As presented in Figure 2 and Table 3, the respondents believe that Ljubljana should promote cultural (67.08%), green (48.45%), and sports (37.89%) types of tourism the most, in line with sustainable urban tourism development. In addition, informants also encourage the development of gastro tourism (23.29%), party tourism (16.46%), senior/intergenerational tourism (15.84%), educational tourism (12.42%), shopping tourism (12.11%), and nautical tourism (10.87%). Less than 10% of respondents recommended family tourism (7.14%), business/industrial tourism (4.66%), medical and congress tourism (both 1.55%), wellness tourism (0.62%), and political tourism (0.31%).  To get an in-depth insight emphasizing the complexity of the context-rich data, the selected proof quotations are presented in Table 4.   To get an in-depth insight emphasizing the complexity of the context-rich data, the selected proof quotations are presented in Table 4. " . . . due to the disconnection of people, Ljubljana remains closed, Ljubljana lacks variegation and diversity, we are not sufficiently aware of our culture and cultural heritage. People need to be addressed with stories, we must emphasize our identity, crafts, history, and culture, it looks like we overemphasize sport and underemphasize culture. We have good projects, but we need to advertise them more [ . . . ] For example, Ljubljana could gain and earn a lot from foreign guides, as for example, if you are a local guide, you have to have a license to guide around the city, meanwhile foreign guides can walk around the city worry-free, without licenses, and that should be changed, we could earn extra money here."

Quotation 4 Respondent 24
" . . . inaccessibility of the parts of the city for disabled, we need more drinking water fountains, more public toilets accessible also for disabled people, we need to emphasize and promote local food, open a restaurant with local food and drinks atČopova street."

Quotation 5 Respondent 36
" . . . more sports events for all generations, introduce the Gladiator event in Ljubljana, to revive the Koseško pond, to be able to rent pedal boats for a ride at Zbilje lake, to organize more outdoor cinemas (in Tivoli, at the Congress square, etc.), better promotion of Ljubljana, greater connection of the residents by for example exchanging items or garage sales."

Quotation 6 Respondent 38
" . . . adapt Ljubljana for short city breaks, by offering more shopping centers, more active experiences in Ljubljana and more romantic experiences in Ljubljana. The need to emphasize architecture with the focus on Plečnik, more fun events, more experiences of Ljubljana by night."

Quotation 7
Respondent 41 " . . . Improved marketing with the emphasis on the analysis of tourists' expectations, more youth benefits in terms of additional offers and guides around Slovenia divided by their age to have a peer as a guide."

Quotation 8 Respondent 123
" . . . more green areas, elimination of traffic jams, better traffic connections with Ljubljana, more information on events in Ljubljana, a place where I will feel a sense of belonging to Ljubljana."

Quotation 9
Respondent 127 " . . . higher number of festivals, a product through which a person could experience Ljubljana from the past, more parking spots near the center."

Quotation 10
Respondent 178 " . . . higher number of concerts in the center, better signage of the sights, the route of Roman Ljubljana, some great attraction"

Quotation 11 Respondent
" . . . increased supply of vegan food in a trendy restaurant increased supply of local fruits and vegetables at a more affordable price, more fruit trees, not only ornamental ones but also the edible ones. Multiple urban installations by the principle of Prostorož or Light Guerrilla. I want a playground with endless trampolines." Source: own.

Discussion
Our paper further integrates two scientific fields, namely, sustainable urban development as well as sustainable tourism development. Till today, four scientific articles have been published on sustainable urban tourism development according to the Web of Knowledge Core Citations database, namely [13][14][15][16], which indicate that the scientific field of sustainable urban tourism development is emerging, yet it needs further advancements. The proposed conceptual model contributes to the understanding of sustainable urban tourism development by (a) integrating existing unidimensional models of sustainable urban tourism development [13,14] into a single multidimensional model and (b) expanding the model to include different types of tourism as suggested by sustainable tourism development literature and incorporating the management process dimensions to reflect the fact that sustainable urban tourism is an ecosystem that needs to be properly managed. The resulting expanded model of sustainable urban tourism development encompasses four levels on which sustainable tourism occurs: dimensions of sustainability, stakeholders of sustainable urban tourism development, type of tourism to be promoted, as well as the management process. The overall validity of the model is illustrated by applying it to the case of Ljubljana.
The presented model should be understood in 3D visualization technique and, at the same time, serve as a building block for further adjustment of the model by adding: (a) additional dimensions of the sustainability, e.g., technological [79]; additional stakeholders, e.g., key publicand private-sector stakeholders [31]; additional types of tourism, e.g., adventure tourism [80]; or (b) additional layers relevant for sustainable urban tourism development, e.g., possible threats, as, for example, overtourism [44], water pollution [81], and others; or existing conditions, e.g., developed infrastructure, existing legalization, financial viability, and others, which are all possible avenues for further research; or (c) by adapting the proposed model for sustainable non-urban tourism development, e.g., rural [82] or mountain tourism [83]. Respondents grasped the sustainability concept in its integrity: 43 (13.35%) mentioned in their conceptualization all three studied sustainability elements (economic, social, environmental). A test of the proposed model on the case of Ljubljana, based on 322 informants, shows that Ljubljana should develop cultural, green, and sports types of tourism the most, next to the gastro, party, and senior/intergenerational tourism, in line with UN sustainable global goals and practices. Ljubljana offers, for now, yet-unfulfilled potentials also in experiential nautical tourism [84].
The management process needs to be professionally incorporated into the daily functioning of SUTD. It is necessary to involve and mobilize citizens and expand the specter of key stakeholders in sustainable urban tourism by capturing and better communicating the impact of that kind of tourism. Policy-makers need to show what is the impact of sustainable tourism in urban development and if other cities are less developed due to traditional tourism focus. Cities need to indicate and share with key stakeholders a clear direction of sustainable urban development which has mission-driven financing and incorporates bottom-up advancements of inhabitants and tourists.
Resilience measures need to be incorporated into sustainable tourism and future planning [85]. The paper discusses one option of managing SUTD by incorporating and developing different specters of sustainable tourism types by integrating different sustainability aspects and stakeholders. Today, tourists do not want to feel and be seen as tourists, rather, they want the feeling of belonging and inhabiting the place they visit or stay at in order to get an authentic experience in line with circular economy [86], new platforms Airbnb, Couchsurfing, global sustainable tourism trends [87].
A sharp distinction exists between traditionalists and modernists in the policy-making arena in the major cities: those who agitate against tall buildings, and those who promote them under the banner of urban sustainability should be avoided [88]. Industry and academic points of view need to be considered in the formulation of any urban tourism research agenda. Here, education and training are strategic factors for SUTD [89]. Also, corporate social sustainability needs to be the basis in the educational and training programs in tourism, overall, not just specifically in SUTD [90].

Conclusions
The theoretical contributions of this study are multifaceted. The first theoretical contribution to the scientific research area of sustainable urban development [27] represents an up-to-date literature review. Numerous scientific articles have been published in the Web of Science Core Citation on sustainable urban development and the analysis [24,36] shows that this construct is becoming extensively researched since 2011. Moreover, researchers from different fields bring theoretical contributions by wearing different lenses, ranging from environmental sciences, regional urban planning, geography, construction building technology to urban studies, economics, management, transportation, and energy fuels.
Second, a similar theoretical contribution is identified also in the sustainable tourism development field. Analysis of Web of Science Core Citation scientific articles shows an increased interest in sustainable tourism since 2008. Sustainable tourism research attracts researchers from social sciences, engineering, geography, public administration, education, urban studies, computer science, and others. Searching for solutions, it is important to combine the multifaceted perspectives of the research constructs as existing studies, as focused on only topics within their own "silos" domain, and horizontal collaboration among disciplines is necessary for innovation and new research findings to be implemented.
Third, the originality of this work lies in the integrated and advanced multidimensional conceptual model of SUTD, which is applied to the Ljubljana urban area. Managers (city governors) need to take into consideration different perspectives when developing sustainable urban tourism, and our proposed model shows how to do so by combining different perspectives. It serves as a basic platform which should be modified and therefore upgraded by additional dimensions for each specific area. Our proposed model can also be modified and, as such, applied to other touristic areas, such as rural, mountain tourism in line with sustainable development. The practical value of the proposed model is for interested stakeholders, who should carefully rethink the types of tourism and possibly add other new types that are emerging or present in their specific context. In doing so, it is important to visualize this model as 3D, so it offers the basis for considering different possible combinations the model enables by rolling all or some "circles." Nevertheless, other layers/dimensions can also be added to the proposed model. For example, within the layer of sustainability dimensions, technological sustainability [79,91,92] also plays a role, and resource dimension [27] can be added.
Nevertheless, we think this study is an important step forward when bridging the two studied fields, sustainable urban development, and sustainable tourism development, by offering an integrated and advanced conceptual model of SUTD. In order to ensure sustainability in the future, the urban areas, as well as tourist destinations, need to develop in a sustainable manner.
When setting the guidelines for future sustainable tourism development following the proposed model, the stakeholders, such as city governors, decision-makers and researchers, can learn from the model how to integrate the proposed dimensions and consider all possible combinations of tourism development based on the designed model by spinning the proposed layers of the conceptual model. In addition, additional layers could also be added as, for example, type of accommodation, duration of stay, and other elements they want to include in their final touristic product/service/study offer if interested stakeholders find it necessary. We conceptualized our work based on the gap that there is no integrated model for developing SUTD and connected existing models into our model where every layer represents another aspect of SUTD, and city governors need to take into their consideration all of the layers when they are deciding how to develop and manage their cities further. The field of tourism in the urban environment needs integration [43]. Our model's aim is to offer structure, but not as "a straightjacket," and enable the foundation for further theoretical and empirical research [43].
In line with the recommendations [93,94], managerial implications for Ljubljana SUTD governance, such as policy-makers responsible for Ljubljana, sustainable development should put more effort on managing the heritage value of tourism destinations for strategic management, integration of databases (vertical and horizontal), as well as the marketing purposes. Looking just at Europe, 73% of Europeans live in cities [95,96]. Our model is worth studying and adopting for cities which wish to have a conceptual tool for integrating all the smart solutions in their cities that modern technology nowadays can provide; however, city governors need a strategical guideline on how to integrate the data and tools acquired in order for them to be sustainably managed in neighboring cities, such as Vienna [97], Torino [98], or other global emerging smart cities.
Despite the abovementioned theoretical contributions, our study has some limitations due to the characteristics of a chosen research approach-qualitative study, as it does not allow for statistical generalization. The interviews were performed in the Slovene language, and some meaning could be lost in translation. Also, the majority of the literature review is based on journals in the English language. Nevertheless, the proposed conceptual model is applied to a single case study and additional case illustrations could be performed to further advance the model. We also recommend applying the proposed model to other urban settings as well as by adopting it, to apply it to the nonurban environment. In combining the research areas-sustainable tourism development and sustainable urban development-we recommend further study of the emerging research trends by the integration of studied research areas, as it may bring important theoretical as well as practical implications for this, as well as for future generations. Nevertheless, sustainable urban tourism development needs to enable quality places for people to live and also to visit [16], no matter the companies' size or the budgets [48]. Funding: This research was partly funded by the European Social Fund, Javni sklad Republike Slovenije za razvoj kadrov in štipendije, Republika Slovenija Ministrstvo za izobraževanje, znanost in šport, "Naložba v vašo prihodnost," operation is partly funded by the European Union, European social fund. The authors acknowledge that the paper was partly financially supported by the Slovenian Research Agency, Program P5-0364-The Impact of Corporate Governance, Organizational Learning, and Knowledge Management on Modern Organization.