ENA sustainable city can be defi ned and understood from several perspectives. The classic perspective defi nes it as a city where its social, economic and natural realms develop in a balanced way. On the other hand, there is also another perspective which is based on 17 SDGs for 2030 set by the UN General Assembly in 2015. In this research, an additional perspective was implemented by authors of diff erent scientifi c fi elds who investigated the urban sustainability phenomenon based on a balance of social (“human”) and spatial (“physical”) realms and their change over time. The focus of this research is on the change of form and function of open public spaces in post-soviet modernistic districts. The aim of this paper is to present and discuss the methodology and results of the research, provide insight regarding the usage of public spaces and attempt to determine the trends and challenges in the usage of open public spaces which also have a direct impact on the quality of life in the cities of urban sustainability.Several methods were employed to collect the data in the second largest city of Lithuania – Kaunas, such as content analysis, statistical analysis, and sociotope analysis. Such a complex methodology resulted in the collection and systematic analysis of the real interests and needs of local public space users. It can be calibrated and applied to study and develop cities undergoing complex social and spatial transformations. It was concluded that improving certain forms and functions of open public spaces would create new possibilities for local users to spend more quality time in nearby open public spaces, which in turn would lead to the creation and strengthening of closer interpersonal relationships, identifi cation and representation of shared interests, sharing of resources, and creation of a stronger local community, thus contributing to a sustainable development of the neighbourhood, the city, and people who inhabit in these places. Keywords: urban; sustainable development; open public space; sociotope methodology; post-soviet cities.