For the first time in history, half of the worlds population is living in cities, and not just in cities but in mega-cities. Never before have we confronted such a geography of the world's people. It is a phenomenon which holds out enormous possibilities and at the same time poses problems, on a scale unknown befoe, of social organization, democracy and sustainability. Drawing on our spatial imaginations, City Worlds prompts a distinctive understanding of cities. Exploring how different worlds within the city are brought into close proximity, this book demonstrates that cities in the world are essentially open, their very dynamism being a function of their interconnectedness. Analysing cities through this spatial understanding, City Worlds outlines new ways to address soem of the ambiguities of cities: their promise and potential, theior problems and threats. the argument in the Understanding Cities series. Using an integrated and interactive text City Worlds draws on our spatial imaginations to prompt a distinctive understanding of cities The authors outline new ways to address the ambiguities of cities; their promise and potential, their problems and threats.