Drawing on the arguments of the sociologist Eric Klinenberg, this article develops the concept of “social infrastructure” as a way to research and value these kinds of spaces. Social infrastructure helps in recognising the public dimensions of often overlooked and undervalued spaces. It draws attention to the breadth, depth, and textures of sociality that can be afforded by different urban environments. In developing the concept of social infrastructure, this article pulls together four related strands of social scientific inquiry: work on infrastructure; publicness and public space; sociality and encounter; and the politics of provision. An infrastructural approach to the topic of public space presents geographers with some productive tools for understanding the public life of cities.