3San Francisco is home to more than 800,000 residents and hosts more than 17 million business and leisure travelers each year. But few visitors--or locals, for that matter--realize that there are more than 220 premier parks and 70 miles of hiking trails in the city itself.

Urban Trails: San Francisco is the only guide available that details so many trails within the boundaries of the city, including mainland San Francisco and the city's four islands: Alcatraz, Angel, Treasure, and Yerba Buena. With a focus on parks and trails, here you'll find 50 routes for walkers, runners, and hikers. Other features include:

• Trailhead directions, including public transit options
• Info for families and dog owners
• Trail distance, high point, estimated time, amenities, and more
• Sidebars on area history, nature, tips, and sights