For a quarter of a century, the architectural collective raumlaborberlin has been pioneering new spaces for action, charting unique paths in cooperative urban development, and creating places to foster encounters. Together with experts across various fields, they explore forms of urban practice, participation, and the joint production of space. Polylemma tells the story of this work: its nine members visit the sites of their work, come together with long-standing colleagues and critics, dissect the mechanisms behind their actions, and reflect on the tools and methods of their research-based practice. Topics discussed across numerous projects include strategies for learning together, experimental building, and radical recycling. Polylemma challenges us to open up our notion of space. How do we want to live together in the future? The book is a plea for the city as a sphere of action.