The social morphology of German cities changed dramatically during the 20th century. The segregation of private and public space was typical of this process. Being motivated by social and sanitary reasons, public intervention removed semi-open ways of living (halboffenes Lebensformen) and destroyed the old slums. At the turn of the century, a process of domestication (Verhaeuslichung) began, which changed urban communication structures as well as daily life in the cities. Thus, the social morphology of the new urban space was the result of the interaction of two forces: the functional differentiation of urban space and the development towards the closed culture of modern private life.