. Full-color guide to 50 trails, many of them within city limits . Routes rated for fitness for walkers, runners, and hikers San 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