Inferences about the determinants of land prices in urban areas are typically based on housing transactions, which combine payments for land and long-lived improvements. In contrast, we investigate directly the determinants of urban land prices within a metropolitan area - the San Francisco Bay Area. Our analysis focuses on the relationship between the regulation of urban development within different jurisdictions and land prices, while considering other factors that shape the value of land, such as topography and access to jobs. We find that cities that require a greater number of independent reviews to obtain a building permit or a zoning change have higher land prices, ceteris paribus. Finally, we relate the variation in land prices to the prices paid for housing in the region and show that local land use regulations are closely linked to the value of houses sold. This is in part because regulations are so pervasive, and also because land values represent such a large fraction of house values in the San Francisco Bay Area.