As the majority of us are now urban dwellers and cities consume the bulk of global energy, it is time to re-evaluate the spatial and political models that shape city growth. Drawing on comparative research on world cities like Sao Paulo, Mumbai and Johannesburg the lecture explores how the physical and the social are deeply connected, reasserting the role of architecture and design in 21st-century city-making.Ricky Burdett is chief adviser on architecture and urbanism for the London 2012 Olympic Games and Centennial Professor in Architecture and Urbanism at the London School of Economics. He was Director of the 2006 Venice Architecture Biennale and is co-editor of The Endless City (Phaidon, 2008).