Responding to raised concern that the various processes of neo-liberal restructuring are threatening democracy, this chapter critically interrogates the agency and instrumentality of space in encouraging/enabling or discouraging/suppressing democratic processes, actions and behaviours. It investigates classical theoretical perspectives on the relationship of the spatio-material and socio-cultural, foregrounding urban spaces and issues of social and environmental justice, as framed by Lefebvre’s ‘right to the city’. A framework and set of four lenses to understand, critique and operationalise the democratic potential of urban public space is proposed. These are applied to critique three examples of designed public urban spaces representative of particular approaches. A new alternative approach to the understanding and design of spaces based on ‘assemblage’ as a theoretical and conceptual framework is developed, holding potential to realise the ‘right to the city’ and to counteract the post-political erosion of the urban public sphere associated with austerity and neo-liberal governmentality.