The devastation brought upon New Orleans by Hurricane Katrina and the subsequent levee system failure has forced urban theorists to revisit the fundamental question of urban geography and planning: What is a city? Is it a place of memory embedded in architecture, a location in regional and global networks, or an arena wherein communities form and reproduce themselves? Planners, architects, policymakers, and geographers from across the political spectrum have weighed in on how best to respond to the destruction wrought by Hurricane Katrina. The thirteen contributors to What Is a City? are a diverse group from the disciplines of anthropology, architecture, geography, philosophy, planning, public policy studies, and sociology, as well as community organizing. They believe that these conversations about the fate of New Orleans are animated by assumptions and beliefs about the function of cities in general. They unpack post-Katrina discourse, examining what expert and public responses tell us about current attitudes not just toward New Orleans, but toward cities. As volume coeditor Phil Steinberg points out in his introduction, “Even before the floodwaters had subsided . . . scholars and planners were beginning to reflect on Hurricane Katrina and its disastrous aftermath, and they were beginning to ask bigger questions with implications for cities as a whole.” The experience of catastrophe forces us to reconsider not only the material but the abstract and virtual qualities of cities. It requires us to revisit how we think about, plan for, and live in them.