Urban playgrounds form a vast, intricate spatial and social network. They are places where material innovation happens and stages for new professional collaborations that carry a wealth of social, spatial, and climate- and nature-positive design potential. This book documents more than 200 playgrounds throughout the city of Rotterdam, recording and reflecting on the accumulated urban environment of play. Through interviews with playground makers, designers, and urban thinkers, it gathers insights while bringing attention to emerging progressive practices, concepts, and ideas. PLAY! marks the beginning of a dialogue about possible futures of urban play landscapes.