Public space is a frequent theme in recent writing about cities; scholars describe ways in which urban activities, histories and identities are prescribed, controlled and homogenized. Yet, everyday urban dwellers encounter spaces that are loose, that manifest great variety and unpredictability, which simulate imagination and intervention. Loose spaces are places of possibility. What sets this book apart is that it is first and foremost a book about physical spaces, their capacity to shape and support behavior. It is aimed at readers who are interested in spaces: how they look and how they work and how urban space can serve social life. It provides a series of general speculations on how the task of design might address those parts of the built environment that are undersign or under designed.