The article presents an analysis of participatory urban planning practices in the context of their impact on providing the city with advanced high-quality public spaces. The case of the Heroes of the Heavenly Hundred Square in Zhytomyr shows the positive impact of urban activism on improving the quality of abandoned public space by means of its reconstruction. The assessment of the quality and the use of the Heroes of the Heavenly Hundred Square after the reconstruction was conducted on the

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... s of calculations of indices specifying an intensity of use and, in particular, social use, duration of stay of visitors, variety of use and users, and time variety of use. The indices were calculated based on the data collected during the structured observation. The results demonstrate that the square is characterized by a moderate level of intensity of social interaction, high level of intensity, variety and time diversity of use, as well as very high level of user diversity index. Eight areas by the location of different types of square visitors activities have been identified according to the results of observations and surveys; in particular, it is revealed that the areas of chess tables, a cafe, playground and various benches are in the greatest demand in the square. The inclusive accessibility, comfort and safety of the square after its reconstruction are analyzed. It was found that the high social intensity of the Heroes of the Heavenly Hundred Square use show its sacredness for citizens as a place of memory, a place of identity formation, a place that attracts visitors, and a place that encourages Zhytomyr residents to go out to the city. The study of the impact of urban activism on improving the quality of the abandoned public space (the Heroes of the Heavenly Hundred Square in Zhytomyr) contributes to the discourse on modern transformations of public spaces in the cities of post-socialist countries.