Mass housing in Germany, Russia, and Ukraine represents an enormous volume of housing today and therefore a huge resource for the future development of cities. But transformation of these districts is needed due to the functional, societal, and technical problems and challenges they face. How can sustainable, socially compatible, ecological responsible, and economically efficient development be achieved? The book summarises the results of a three-year research project. Based on the selected case studies, it points out the qualities and values as well as the problems and potentials involved in spatially transforming prefabricated housing estates from the 1960s and 1970s. The specific features and characteristics of the socialist city are evaluated with respect to their potentials and difficulties, and with regard to the requirements placed on future district planning and development. Hence this book contributes to the on-going discussion and serves as a valuable basis for developing planning strategies.