Heidegger was challenged by spatiality. He attempted to ground space in time and while he gestured toward nesting one in the other, ultimately (as he even later admitted) it was a failed attempt. While space remains confused, room is added to the notions of place and region.
Room is at a finer scale than place which is a finer scale of region. Room "is the staging arena for more precise and delimited operations in particular places" (Casey, p. 258). Somebody can make room for themselves. Room is constituted through somebody shaping various leeways about their own body. Heidegger makes these moves in section 70 of BT (p. 420): "To Dasein's making room for itself belongs the self-directive discovery of something like a region….Concernful being-in-the-world is directional--'self-directive' (sich ausrichtend), it is responsible not only for the precipitation of place but also for making of room (and its leeway) and for the discovery of region." This means that in the event of being-in-the-world somebody makes room for themselves. In taking up room somebody carves out the room for themselves by displacing their own leeway. And being the beings that get preoccupied in the role somebody is playing, humans inscribe place in the displacement of carving out room for themselves. The inscription of place thereby characterizes and makes the discovery of region possible.