Move over cable cars—San Francisco is a town best explored on foot. The compact city is 7 square miles (18 square kilometers) of dense neighborhoods, historic alleyways, hilltop viewpoints, and urban green spaces. While San Francisco walking tours are great for experiencing the unique character of city neighborhoods—and even a certain world-renowned bridge—they can venture beyond the beaten trails that bus tours rarely tread. They're also often organized around themes such as architecture, hiking, street art, cuisine, history, and even ghosts.