The antic city walls of Istanbul are a territory of informal uses, in three registers : housing, economic activities, and daily social practices. Despite discourses and sporadic actions of reduction, these uses do go on, because of their regulation role in economic, urban, social, psychological and symbolic matters. Practical compromises are built by the different agents, both users and authorities, to maintain these "valves" of the urban and social life – recognized useful but not legitimate. A chronicle of the fifteen last years allows to compare the remaning stabilities and resiliencies with some evolutions in those process during the recent actions of the urban renewal operations.