The paper is part of a thirty-year study of Piazza Maggiore, Bologna, that sees the piazza as a natural ecology. Using the flow of water as a metaphor, I examine how the piazza functions as a passage through the city, with locales inside and adjacent that serve several purposes and several functions. Nooks and crannies in and around the piazza serve as “eddying pools” and “meanders” and boundaries inside the piazza from old sidewalk and street makings become boundaries and channels. The activities in these regions of the piazza have evolved over time, as seen in the photos made during the intensive but intermittent visual ethnographic field work undertaken on thirty visits to Bologna.