Proposing that space shapes publics and publics (re)shape their own spaces, this dissertation explores how the sociopolitical construction of public space informs planning, design and space-making processes. Ethnographic fieldwork including participant observation, direct observation, interviews with key actors and videophotographic analysis documented two social movements, the 15M mobilizations in Barcelona (the Indignados Movement) and Occupy Wall Street in New York City, whose protest encampments and occupation of public spaces became means of expression, organization and resistance. Fieldwork suggests that these movements rejected representative democracy and representative economy and refused representational processes in their assemblies and forms of organization. They enacted a politics of direct presentation in public space rather than re-presentation. Part One explores how the social movements constituted themselves as new publics in space. Part Two demonstrates how these newly constituted publics constructed their own spaces. Part Three draws lessons about how to plan and design public spaces through space-making processes used in these encampments. The protest encampments operated as open spaces permeable to diverse physical, organizational and informational inputs from outside. Welcoming newcomers at all times, they developed an aggregative identity in perpetual transformation as true spaces of becoming in which the public and the space continually transformed and reinvented themselves. Like open-source or wiki systems, the social movements and their encampments operated through approaches of open planning. Implications and applications of such approaches for planning and urban design involve thinking of planning as a truly open-to-the-public process incorporating citizen participation in situ and in real time, with potentially enormous effects on city-making. iii