Cities are the locus of global economic dynamism. Urbanization in emerging nations, the growth of high-technology clusters in superstar cities, and the rise and fall manufacturing centers combine to create a global hierarchy of cities, linked by flows of ideas, people, and trade. Although urban density fuels economic growth, it also facilitates disease transmission, as evident during the Covid-19 pandemic. We begin the course by discussing the costs and benefits of urban density, which explains how cities form and develop, why innovative firms concentrate geographically, how communication and transportation networks shape urban systems, and how disease can upset this balance. We next address key policy issues confronting cities in both advanced and emerging economies, including urban sprawl, affordable housing, place-based policies for struggling regions, rising income inequality within and between cities, reducing the carbon footprint of urban living, and mitigating the risks of disease transmission within and between urban areas. The course highlights big-data approaches to urban economic policy analysis and involves a mix of slide presentations, in-class lab exercises and policy debates, and team assignments. Students will complete a paper of their own design in which they will propose solutions to a policy challenge confronting a particular city or region.