We chose EC 120. It turned out that it was in fact not quite big enough for the three seminar groups of a dozen students to meet simultaneously, but we found it possible either to stagger such meetings or to find empty rooms or other meeting places on an ad hoc basis. In EC 120, it was possible to arrange the room so as to foster various kinds of interaction -- groups of two tables around which six students could work comfortably, a large circle for whole-class discussions, an open circle for inkshedding, three assemblages of six tables for seminar groups, etc. Often, before a meeting, we would arrange the room in advance. As the year progressed, everyone came to think of the room as flexible space, to be arranged as needed, and students would often rearrange it for their own purposes. Perhaps more important, the room came to be seen as "home base," a place where people could meet and work or converse as needed (at least on Tuesday and Thursday).