Complex socio-economic transformations have left a significant impact on the physical realm of many post-soviet cities resulting in declining living qualities, abundance of massive industrial sites and urban sprawl. Recent attempts to improve the situation are targeted mainly towards regenerating areas close to the city center. However, in many cases regeneration does not guarantee the vitality of these areas and success of the projects. In reality new plans tend to neglect social and economic complexity of renewed areas by replacing these structures with developments profitable for real estate companies. The extension of the international business district together with redevelopment of Calvary market area in Vilnius is one of the examples of such trend. What is more, plans of redeveloping areas in the city center are fragmented and are not contributing to create the overall vision for the center, or focus on social integration and creation of vital and diverse city life, instead the plans might trigger creation of gated communities and large scale retail centers that have negative impact on vitality of this area. This project aims to find ways to develop areas in the city center of Vilnius by integrating the informal market as a generator of vitality for new interventions. There are several projects concerning development of complex structures in the context of post-soviet cities carried out under Metropolitan Spatial Structure research theme in, TU Delft. However, one could recognize a certain gap in lack of insights on the aspects of vitality in these cities. This particular thesis aims to contribute to the mentioned subject while researching the conditions of vital city life in post-soviet context as well as the spatial structure of Vilnius and its center. The conclusion derived from this research will be used to formulate design guidelines for specific area of the city – CBD expansion and Calvary market zone. Intended outcome of the project is the vision for the city center and design proposal for a specific area, in result this project could be used as an example of developing complex structure in post-soviet city.