In Istanbul, public university hospitals exemplify the importance of urban social networks in the structuring of economic activity. The involvement of patients' families in care-giving on hospital premises is essential to the efficient functioning of the health service. This paper illustrates the vital role of cultural and social factors, especially kinship relations and informal networks, in shaping the urban built environment at the local level. The paper shows how family solidarity is a precondition for the successful functioning of a major city hospital in Istanbul, and how this affects the economic character of the built environment around the hospital. The paper employs a relational approach to highlight to key processes at work.