3. Results
3.1. Validation of the Syntactic Models Based on Compatibility to Form Fits Function Principle
Several indicators from the Visual Graph analysis (From VGA) and additionally conducted axial graph analysis were selected for validation of the modeling results while looking for some logical coincidence of syntactic and functional patterns. The aim was to see if at least some of those clear overlapping could be observed and if models are sensitive to the essential differences of the investigated cities.
From VGA the following metrics applied: Connectivity - measures the number of visual connections from a specific point where bigger numerical value means bigger area of the isovist visible form the point; Point Second Moment - evaluates the distribution of visible distances, determining spatial homogeneity or heterogeneity where higher numerical values mean less compact form. It is counted in a similar way as the Point First Moment described earlier, just with values squared. The indicator could be seen as a one combining occlusivity and connectivity – it was not used in the modelling of the features of acceptable environment but found useful for more generalized comparison of functional and syntactic zones.
The Axial analysis which is based on modeling of visual axes was used as additional tool for validation. It was chosen over the most often in space syntax modelling of urban structures used segment analysis as more suitable in the presented case because of the focus of the presented research on visibility, relatively small size of the investigated urban areas where topological distances are at least of equal or even higher importance then metric distances, and, at the same time, simulating concentration of people, movement, etc. Metrics applied: Relativized Entropy (further Entropy) - indicates the diversity of routes and navigation choices, for the mathematical definition, see Hillier et al. [
40] p. 365 and Turner [
28] p. 8. In essence the biggest entropy shows the most hidden, potentially the most private areas of the spatial structure which are the most hard to find accidentally. Intensity - assesses reachability potential in key locations presented in normalized form, “It also aims to capture the movement efficiency given the distance one must travel in the network” [
41]. As it is an alternative and more precise for calculations of integrations - the most reachable areas in urban structures which, if the model is working well, should coincide with the most functionally intensively used, the most important key areas of the spatial structure. Choice - measures how frequently certain segments are used as the shortest path [
40]. If the model is working well, high choice values should overlap with the main transit streets.
City and Building Plan Analysis:
Elektrėnai. Visual Connectivity: the strongest visual connectivity was observed at the main city entrance junction thus reflecting importance of symbolical spaces which could be called “city gate” (
Figure 2). Importance of those spaces could be confirmed by sculptural composition “Elektra” located at the main entrance to the city. Point Second Moment: courtyards of multi-story buildings were homogeneous, with relatively little variation between near and far visible points. It corresponds to observed facts that even while applying concepts of modernist urbanism in Soviet Lithuania, the attempt to make courtyards of multi-flat houses more private and compact, was made. Of course, it does not mean that modernistic courtyards were as compact and homogenous as some spaces of the medieval city - for such comparison normalization of values would be needed as discussed in the methodology section, but spatial allocation of not normalized values correspond to in situ observed differences in character of public spaces of the city. Building plans revealed the strongest visual connectivity at staircase junctions ("apartment crossroads") and the weakest in sanitary facilities.
Sfax (Tunisia). Visual Connectivity: strong connectivity was observed at a single point – the religious center with a prominently expressed main street. Point Second Moment: high heterogeneity was noted near market areas, with significant differences between points located close to each other. Entropy: the street network demonstrated high values thus reflecting the functional hierarchical zoning of public spaces: public with the least entropy and semi-private, located deep inside living quarters with the high entropy. Choice: In essence only the real main streets which connect city gates and the main objects as Mosque and Souks, demonstrate high values. The low values in the living quarters correspond well to the attempt to avoid concentrated transit flows there. Intensity: high reachability or closeness was observed at the most important (around Mosques, Souks) zones. Building Plans: centralized layouts dominated, with living rooms-coyourtyards serving as hubs connecting other spaces. The center exhibited strong visual connectivity, contrasting with the corridor-based street network.
Krakow (18th-Century City Plan). Visual Connectivity: a strong connection was observed in the Town hall/ Market square, characterized by high intensity of the axial map as well thus demonstrating overlapping patterns of syntactic indicators and higher functional importance. Entropy: the lower part of the city, particularly Wawel Castle with some peripheral streets in the southern part of the city, stood out as the hardest to find zones. In the case it reflects real situation: more quiet and specialized character of the peripheral streets and allocation of the castle which gives it certain degree of both functional and compositional autonomy supporting its role as the strongpoint for defense against potential attacks from outside as well as from inside. Such patterns of allocation of palaces and castles could be observed in many medieval cities. Point Second Moment: streets exhibited high values due to the straight corridor-like street network. “Closed” gothic squares with streets entering their corners, showed low values, indicating spatial homogeneity with minimal differences between near and far points. Choice: low in squares but slightly higher in streets and especially high in the main streets connecting the main city points: some gates, Town hall square, Wawel. Building Plans: visual connectivity within buildings was not very much differentiated but correspondence of slightly higher values in the man living rooms was noted. The Point Second Moment metric indicated high heterogeneity in some building corridors or connecting spaces and could be associated with the need to make space clearer in terms of visual navigation.
This analysis revealed the spatial characteristics of the three cities which corresponded to the results of space syntax modelling:
- -
Elektrėnai: Strong visual connectivity in key nodes thus possible representing car-oriented city plan with representative spaces at the entrance points and buildings, emphasizing spatial homogeneity and uniformity.
- -
Sfax: Centralized religious and market areas contrasted with corridor-dominated street structures.
- -
Krakow: syntactic modelling clearly correlated or overlapped with the mani functional zones and streets quite well representing dual functional patterns constructed based on segregation of Town hall square and the castle.
Contextual Framework. The analysis was guided by Nikos A. Salingaros's architectural principles [
42,
43,
44,
45], emphasizing:
- -
Hierarchy and Structure - connections between networks and scales.
- -
Fractal Design - repeating patterns across scales.
- -
Information Richness - the importance of detail and complexity.
The more detailed aspects demonstrating peculiarities of the investigated spatial structures were offered and evaluated by the authors in a 10 point scale where 10 means strong presence of analyzed spatial features.
Table 1.
Subjective analysis of three cities using Nikos A. Salingaros's architectural principles [
42,
43,
44,
45]
.
Table 1.
Subjective analysis of three cities using Nikos A. Salingaros's architectural principles [
42,
43,
44,
45]
.
Architecture Principle |
City and Compatibility (1-10) |
Hierarchical Structure and Scale Relations |
Krakow, Poland (8); Sfax, Tunisia (9), Elektrėnai, Lithuania (7)
|
Information Richness |
Krakow, Poland (9); Sfax, Tunisia (8), Elektrėnai, Lithuania (6)
|
Fractal Design |
Krakow, Poland (8); Sfax, Tunisia (7), Elektrėnai, Lithuania (5)
|
Human Scale Compatibility |
Krakow, Poland (9); Sfax, Tunisia (6), Elektrėnai, Lithuania (8)
|
Adaptation to Context |
Krakow, Poland (10); Sfax, Tunisia (9), Elektrėnai, Lithuania (7)
|
Biological Analogy |
Krakow, Poland (8); Sfax, Tunisia (7), Elektrėnai, Lithuania (5)
|
Connections and Networks |
Krakow, Poland (9); Sfax, Tunisia (9), Elektrėnai, Lithuania (8)
|
Importance of Natural Light and Forms |
Krakow, Poland (9); Sfax, Tunisia (8), Elektrėnai, Lithuania (6)
|
Resilience and Longevity |
Krakow, Poland (9); Sfax, Tunisia (8), Elektrėnai, Lithuania (6)
|
Focus on User Experience |
Krakow, Poland ((9); Sfax, Tunisia (8), Elektrėnai, Lithuania (7)
|
Total |
Krakow, Poland (88); Sfax, Tunisia (79), Elektrėnai, Lithuania (65)
|
Elektrėnai (Total Score: 65). Human Scale Compatibility (8/10): the city’s layout and building plans are well-suited to human proportions, providing functional and comfortable spaces for residents if compared to the other modernistic cities. Connections and Networks (8/10): strong visual connectivity at key nodes, such as the main entrance junction, ensures efficient movement within the city. Focus on User Experience (7/10): the city provides a functional and straightforward layout, making an attempt to contribute to user comfort. Fractal Design (5/10): The city lacks the intricate repeating patterns often seen in more naturally inspired designs. Information Richness (6/10): the homogeneity of spaces, especially in courtyards and apartment layouts, limits the richness of visual and spatial experiences. Resilience and Longevity (6/10): while functional, the lack of architectural diversity and long-term adaptability reduces its longevity potential.
Sfax (Total Score: 79). Hierarchical Structure and Scale Relations (9/10): a clear hierarchy is evident with the central religious node and main street dominating the layout. Connections and Networks (9/10): the city exhibits a well-connected street network, with significant links between central nodes. Adaptation to Context (9/10): Sfax reflects its cultural and historical context, integrating traditional architectural styles and functional urban design. Information Richness (8/10): the markets and central spaces offer diverse and stimulating environments. Human Scale Compatibility (6/10): while some central areas are well-proportioned, the corridor-like street system can feel restrictive and less accommodating. Importance of Natural Light and Forms (8/10): although strong in religious and market areas, this criterion is less emphasized in other parts of the city.
Krakow (Total Score: 88). Adaptation to Context (10/10): the city’s layout seamlessly integrates historical and cultural elements, including its central hall, Cathedral Square, and Wawel Castle. Information Richness (9/10): the diversity of architectural styles, public spaces, and historical sites ensures a stimulating urban experience. Connections and Networks (9/10): The street and square network is well-organized, linking important city nodes efficiently. Human Scale Compatibility (9/10): the city’s layout, particularly its central areas, provides a welcoming and human-centered experience. Resilience and Longevity (9/10): Krakow’s historical structures and thoughtful urban planning demonstrate its capacity for long-term sustainability. Fractal Design (8/10): while the city exhibits some fractal properties in its street network, this aspect is not as pronounced in building layouts.
In essence it could be concluded that even based on selected analysis of some aspects of the three cities, and expert based evaluation, it looks that the presented models are sensitive to differences of real structure, reflects at lest some essential aspects of functional logis and could be used at least as logical abduction based explaining models.
3.2. Genotypes
The visualized full results of the modeling are presented in
Figure A1,
Figure A2,
Figure A3,
Figure A4,
Figure A5 and
Figure A6 in the Annex 1. In all cases, the results of the calculations are visualized while using a standard deviation size. In such a case 1 standard deviation and more, point out either 15.9 percent of the highest or the lowest values allowing the most important areas for the precise aspect of the acceptable space. The scatterplots with the summarized comparison of the results are presented in
Figure 3 and
Figure 4.
If just urban structures are compared (
Figure 2), then the following results could be pointed out:
Proximity as Integration: The low values in Sfax reflect its labyrinth-like structure and functional specialization (public, semipublic, semiprivate, private open spaces, functional zoning, etc.); medium results in Cracow correspond to a more integrative nature of gothic city plan with more functional and spatially homogeneous structure; high values in Elektrėnai well reflect the idea of modernist urbanism when houses are seen as placed in continuous open space – either park or a field.
Fascinations as occlusivity: low to medium values in Sfax and Cracow demonstrate some kind of controlled, potentially not overloading with visual stimuli, organized in recognizable patterns of high occlusivity features; high values in Elektrėnai speak about potentially overloaded and possible visually overstimulating spatial structure;
Simplicity as PFM: High values in Elektrėnai, low-medium in Cracow, and low in Sfax. In essence, it reflects openness and degree of visual axe-oriented spatial composition. It could be seen as a kind of clearness of the call or information for a movement of spatial configuration or let us call it dynamic simplicity. If plans of cities are compared then it should be noted that such simple axial lines are clearly defined by contrast with buildings, a limited number of from one-point visible axes, and consistent sequence of presentation of spaces “axe after axe” in Sfax and Cracow. In Elektrėnai a lot of potential axes are visible from the same spots.
Simplicity as compactness: high values in Sfax, medium in Cracow, and low in Elektrėnai. If combined with PFM-based form simplicity it shows the degree of introversion of spaces which, because of simplicity, allows one to focus on internal processes with less disturbance from neighboring spaces. We can call it static simplicity.
Refuge as clustering: big values in Sfax and Cracow as a reflection of clearly perceivable
in situ combinations “visible and clearly definable here” spaces in terms of Cullen [
46] and quite “pockets” or outside rooms in terms of Alexander [
47]. Medium values in Elektrėnai demonstrate that modernist urbanism still made an attempt to create quieter or refugee spaces but either closeness is lower or perspectives of visible “there” are much longer if compared to the other two samples. Possibly both are true.
Common fate as through vision: high values in Sfax, medium to low in Cracow, and low in Elektrėnai. A tree-like street network with a small number of alternative movement routes between origins and destinations of movement and clear separation of various functional zones could be seen as corresponding and explaining the logic behind such results in Sfax. Medieval Gothic plan city focuses on creating more equal alternatives for functions, movement, etc. Modernistic urbanism creates the biggest number of spatial alternatives to look and move thus making features of the common fate hardly perceivable and creating competition between spaces.
We can generalize that the proposed indicators quite well reflect essential differences in urban genotypes of three cities with a kind of controlled proximity, fascination, and dynamic simplicity in Sfax and Cracow. Elektrėnai demonstrates a little paradoxical situation in this case with all three features having high values and reflecting a kind of potential visual stimuli overload or unbalanced situation. Strong expression of common fate in Sfax and more alternatives in Cracow, while very “plural” spatial structure in Elektrėnai, etc. It looks like some strongly expressed features are compensated by low expression of the other features in Sfax and Elektrėnai as two radical opposites. Cracow could be seen as some kind of balance between the different features.
What does it mean in terms of biomimicry? Possibly, if extreme maximums would be treated as some kind of less balanced experience, then Cracow represents the genotype which creates the most balanced spaces in terms of perceived features. The question is to which natural landscapes of environments it could be compared? On the other hand, it could not be said that Sfax or Elektrėnai do not possess at least some of those features, but the lack of balance between them is quite obvious.
A comparison of buildings is presented in
Figure 4. The results could be summarized as follows:
Proximity as Integration: Sfax and Cracow living spaces demonstrate in general a tendency of bigger proximity (mean-max) in comparison to the modernistic flats (mean-low). It is interesting as the first two groups are represented by in essence bigger spatial structures if compared to Elektrėnai and demonstrate the significance of spatial organization despite size for proximity perception and possibly for the other features.
Fascinations as occlusivity: high values in Sfax buildings reflect the most sophisticated spatial organization around the living courtyard in the investigated groups of the medieval Islamic living house. Low values in the other cases reflect the very simple yet functional structure of medieval living houses and modernistic Soviet flats
Simplicity as PFM: Medium dynamic simplicity of the Islamic house and medium-high values of the European medieval houses. Low simplicity in the modernistic flats. The modernistic flat low values are a little unexpected as they are based on the so-called corridor system where the ax of a corridor puts the rest of the rooms together, but, probably, the treatment of rooms as autonomous units and employment of the corridors just as spaces for logistics without the other functions might explain that.
Simplicity as compactness: medium to low values in the Islamic house with its sophisticated diverse spatial configuration; Medium to high values are observed in the other cases as living spaces there are organized out of autonomous cell rooms.
Refugee as clustering: low values in the Islamic city thus reflecting its interviewed functional structure, common usage of space (at least by some groups of inhabitants), etc. High-low values in Cracow reflect the focus on autonomous rooms from one side and compositionally important axial connections between them from the other side. High values in Elektrėnai where typical flats could be seen as a collection of autonomous rooms that could be connected by the corridor in one or another way. The shift of this feature could be related to more family as unit-oriented or individual-oriented preferences while creating living spaces as well.
Common fate as through vision: lowest value in Elektrėnai – it reflects well the structure of autonomous rooms which are connected just by narrow functionally oriented space-corridor. Medium values in the Islamic house are a little unexpected because of its focus on functionally and compositionally dominant living courtyards. Maybe it could be related to the need to segregate certain functions in a living structure. Medium to high values are found in the medieval house.
We should note clear genotypic differences in the three groups of living spaces. Regularity or tendency to compensate high values of one feature by the low values of at least some other features could be noted: the modernistic flats are less fascinating as spatial structures, less integrated, and less dynamically simple but offer clearer refugee spaces, etc.
A summarizing generalized matrix with the results of both cities and buildings is presented in
Figure 4. The exact numerical values are assigned to three categories (high, low, medium) while comparing them between themselves for cities and buildings to “decrease the resolution” of the results a little and to make the general tendencies more clearly visible. In all three cases, interesting regularity could be observed between two groups of indicators: if the group of indicators or features made of proximity, fascination, and dynamic simplicity (PFM) is higher in a city then in general it is lower in buildings and vice versa. A more balanced situation could be observed in Cracow again. Such regularity could be explained and interpreted while using the idea of close interactions and combinations of prospect and refuge. We can assume that the optimal situation is when the prospect is not too big or visually controllable and easily observable. It could be explained and related to the concept of positive stress “… otherwise known as good stress or eustress, (which)is the type of stress response that we feel when we get excited.” [
48]. If loosely defining stress as anything that challenges our state of homeostasis, then too big prospect makes a bigger visual challenge and has a bigger potential to cause negative stress. We can logically assume that stress is increased even more if, besides a big and hardly visually observable and controllable prospect no refugee space could be found nearby in an urban or architectural structure. Such a situation is peculiar, according to the research results of Elektrėnai where the only refugee is a private flat. From the point of view of the prospect and refuge combination, the situation is much more balanced in Cracow and Sfax. If analogy with natural landscapes and habitats is used then, from the discussed point of view, Elektrenai is similar to a desert, where if inhabitant leaves his shelter – he/she becomes immediately exposed in a huge space, visible for potential predators from far away and with need to look around regularly. Sfax could be related to dense jungle where inhabitants can easily hide not only in their own shelters but outside them as well. The specific feature in this case is limitation of prospect which can cause that if only visual perception is used then unexpected dangers or predators could be met unexpectedly. Cracow in this case could be seen as an analogy to forest with both medium prospects and possibility to hide relatively easily in many locations both inside a shelter and outside of it. Final note regarding Elektrenai modeling and its results: space syntax visual graph analysis was conducted, as in the case of Cracow and Sfax, based just on boundaries created by buildings. Are the results in this case correct if modernist urbanism puts a lot of attention to greenery between buildings? In order to give precise answer additional modeling at finer scale with trees included would be needed, but few things could be said already:
We can argue that the situation is right in two cases: for the first decade or more years after the construction of Elektrenai when trees were just planted and made no boundaries for visual perceptions; for a cold season when trees shed their leaves.
In summer, three are visually active but still, we should recognize that in a city they form rather perforated but not solid wall, especially when courtyards of the houses were intentionally made intervisible so activities of children or other inhabitants could be observed through the windows, etc. In this situation we can expect a decrease of the maximum values of the isovist properties, but there is a high probability that essential spatial patterns would be not changed.
We can treat the presented results just as an analysis of pura architectural form created by anthropogenic elements.
4. Discussion and Conclusions
The presented results of the pilot research could be discussed and evaluated within a few theoretical frameworks. First of all, the model is based on the concept of the isovists or view shed as it was mentioned earlier [
30]. It could be pointed out that isovist-based analysis of the architectural spaces in essence allows analysis and construction of spatial typologies through the eyes of the user and still could be seen as a kind of rare and innovative approach which opened new perspectives in architectural modeling as advocated by Batty [
49]. Furthermore, the results of the isovist modeling could be and are related to various aspects of human perception through psychological theories. It could be proved by the presentation of the research by Ostwald and Dawes where they analyzed the possibility to combine isovist analysis and Prospects Refugee theory. On one side they concluded that “While the majority of the measures derived from isovists of the Heurtley house (investigated house) appear to broadly correlate with the prospect-refuge characteristics, (but), under close scrutiny they become problematic and, it must be concluded, that none of them are ideal for this purpose. Even those measures like skewness (PFM) and drift (Dynamic aspect of visual space), which might seem to capture some essence of prospect-refuge theory in a simple room, do not work for more complex spaces.” [
50]. At the same time, they agree that “Conceptually, prospect-refuge should be geometrically measurable using some combination of the strength and direction of the outlook (prospect), the proportion of the isovist that is bounded by solid surfaces (refuge), and that which is made up of occluded radials (mystery).” [
50] and propose that “…combined measures must be verified through their application to more complex works of architecture (and urbanism?)” [
50]. More similar attempts were made while applying the Prospect-Refuge Approach and isovists analysis for seat preferences in offices [
32]. Other applications of the isovists model are more related directly to the analysis of logic of functioning of architectural spaces without searching for the specific ties with theories of psychology, validates the model: “We tested each of the metrics across a large sample of office spaces to unearth their relationship to two specific human behaviors: movement and interaction. We found that some metrics such as Visual Mean Depth (represented by Integration in the presented research as normalized version of Men Depth) play an important role for understanding the effects of movement, more specifically that more segregated floors and spaces tend to attract less movement. We also found that of the two activities movement is the easiest to predict, with many of the results applicable both to large-scale analysis but also on a per-site level.” [
33]. Research by Peponis and his concept of the cognitive frame which was applied for the classification of the analyzed building could be mentioned as well [
51].
Within the described context, the presented research could be seen as the logical input into the mainstream of the research as it does the following:
• Continues to investigate possibilities of applications of the isovist analysis for architectural spaces;
• Attempts to relate the results to various theories related to the perception of the environment and not limiting it to just A Prospect-Refugee approach.
• Expands the model by applying it not only for building analysis but for urban analysis as well – it is not often made.
• Applies analysis on different urban-architectural-cultural settings.
• Attempts to relate the proposed models to the biomimicry framework thus expanding possibilities to find more contact points with various theories and researches in the future.
The second theoretical context of the presented research is the investigation of the preferred environment by Environmental psychology. The research with an attempt to identify quantitative indicators of various aspects of the preferred environment as legibility, complexity, mysteriousness, coherence, ephemera, naturalness, disturbance, etc. was made by Ode and Tveit [
52]. While recognizing the significance of the above-mentioned research on environmental psychology, it should be pointed out that:
• Quantitative indicators were based on the usage of GIS-based descriptive data which presents a kind of “top-down” view on the map.
• It was focused on open, suburban, and rural landscapes.
The presented research attempts to continue and expand the above-mentioned approach by investigating urban areas and adding isovist-based, users' visual experience oriented, simulative, and thus having predictive power, methodology. The model could be even more related to various theories of landscape perception in the future [
4].
The third theoretical framework is made by biomimicry investigation. As was demonstrated in the literature review, it could be stated that the presented research attempts to define the otherwise quite general principles of biomimicry in specific, not-so-often investigated urban scale and combinations with environmental psychology.
Last but not least, the theoretical context that should be mentioned is the idea of a city as fractal. According to Batty, it is one of the ways of abstraction of urban space that allows to see a “naturally growing” or organic system [
53]. In this case, the research presented in this article could be seen as a kind of “fractal view” on the investigated urban structures as it does both: investigates potential regularities of relation of the single cell or house interior and urban spaces; models spaces from even smaller cells thus increasing resolution of the model itself.
The usage of the mathematical graph as the methodological base of the modeling creates a few important possibilities:
• It makes the results comparable with the other quantitative data if available to obtain which creates relatively good possibilities for further calibration of the proposed model.
• The simulative nature of the model means that it has not only analytical but predictive powers as well. Such powers could be expanded into two directions: future and past, as it was demonstrated in this research.
• The mathematical basis of the model in essence allows us to combine it or include it into parametric architectural and urban design processes.
Combination of the results with the theoretical framework of biomimicry creates a background to expand the view on urban structures not only while using qualitative indicators, but even generalizing analogies, e.g.: as it was mentioned earlier while comparing the modernist city to a “desert” in a similar manner as Bauman compared center of Brasilia to Gobi desert [
54] and medieval cities to different types of “forest”.
Are the results of the presented model valid? Validation of the model could be approached from three perspectives:
• based on deductive reasoning while stating that if a similar model were confirmed by other researchers, then, it is logical to expect that similar methodology is working in our case.
• Based on abduction logic, which states that if an explanation given by a model looks logical then it should be accepted as right till better results are obtained or the model will be tested based on the other principles.
• Based on empirical data.
In essence, all three approaches were used. First of all, we can point out the earlier-mentioned sources which confirm that graph-based and isovist models correlate with human behavior at least in cities. Secondly, the construction of the model itself was based on both deductive and abductive reasoning. Thirdly – the modeling results were overlapped with the data on the functionalities of the investigated cities and buildings while using the layer overlap method (
Section 3.1). The main idea was that if functional patterns and logic could be related to the obtained mathematical results, then there is a higher probability that the model is working rather than not. The main problem in this case was the availability of data for historical cases about more precise allocation various functions. In essence, it was based just on the present cartographic sources. The same principle was applied in Elektrėnai as even though the Open Street Map data is available in essence it represents just the allocation and density of various objects which could be related to visual perception affecting human behavior indirectly only. Precise data on the movement of people and informal micro-functions of public spaces, possibly based on observation in situ, would be needed. This situation leaves the question of further validation open and should be addressed in future research. As isovists describe a human visual experience in a space then one of the tools for validations could be measurement and analysis of human reactions, e.g., based on eye tracking technology.
In terms of the limitations of the research, the following aspects should be pointed out:
• Three, relatively homogenous cultural and spatial small urban structures were investigated. The question is how more complex urban systems should be modeled.
• Only one type of cell–living house was present in the model, but even in the investigated cities the variety of cells is much higher, e.g., churches, mosques, other public buildings, etc.
• As the review of similar research demonstrated, different interpretations of the features of acceptable or preferred environments by combinations of the visual graph indicators can exist. In our case we used the principle common to all scientific models – it should be as simple as possible. As a result, we made an attempt to find just one indicator if possible, for the description of the features of the visually perceived environment. It means that more possible combinations could and should be explored.
• The need for investigation of various possible combinations of the visual graph indicators for the features of an acceptable environment, requires looking for quantitative methods of validation of the model in the future. As it has been mentioned before, the authors see eye-tracking technology as the potential candidate for this task.
While finalizing it could be generalized, that despite limitations and because of its nature as a pilot study, the presented results demonstrate sensitivity to the different cultural-urban situations and logical correspondence to features of those environments which could be pointed out by the subjective experience of the authors while walking in Elekrėnai, Old Town of Cracow and medinas of the Islamic cities. The results fit into the context of biomimicry investigation and potentially expand the theoretical and methodological framework of the Isovist modeling while using Visual Graph Analysis and relating it to the features of an psychologically acceptable environment.