This article is devoted to the spatial changes in the postmodern, post-transformation city, and particularly to areas that can be defined as the “in-between city” (German “Zwischenstadt”). This term refers to areas characterized by a change of function connected with the extensive spatial development of a city. The authors undertake to present studies of the case of the “in-between city” areas of two cities in Poland (Poznań and Gdańsk) and the various types of participation in culture that occur there. They call attention to the culture-forming and city-forming potential of “peripheral” areas, which are currently intensively urbanized but which not long ago were treated as industrial terrain or as areas for supplying resources (communications routes, energy infrastructure, etc.). The authors seek out the historical facts conditioning the evolution of the in-between city, as well as making use of the data collected during their study. They refer to the findings of the sociology of the city, the perspectives of culture studies, and the premises of a relational theory of culture.