Abstract. In this paper I argue that a qualitative formalization of built environments needs to take into account: (1) the ontological distinction between bonafide and fiat boundaries and objects, (2) the different character of constraints on relations involving these different kinds of boundaries and objects, (3) the distinction between partition forming and non-partition forming objects, and (4) the fundamental organizational structure of regional partitions. I discuss the notion of boundary sensitive rough location and show that a formalization based on this notion takes all these points into account.