For an outdoorsy adventure and some fascinating history, consider a day at this island northwest of Alcatraz. Discovered by Spaniards in 1775 and declared a U.S. military reserve 75 years later, the island was used as a screening ground for Asian, mostly Chinese, immigrants—who were often held for months, even years, before being granted entry—from 1910 until 1940. You can visit the restored Immigration Station, from the dock where detainees landed to the barracks where you can see the poems in Chinese script they etched onto the walls. In 1963 the government designated Angel Island a state park. Today people come for picnics, hikes along the scenic 5-mile path that winds around the island's perimeter, and tram tours that explain the park's history. Twenty-five bicycles are permitted on the ferry on a first-come, first-served basis, and you can rent mountain bikes for $10 an hour or $40 a day at the landing (daily April through October; call during other times). There are also a dozen primitive campsites. Blue & Gold Fleet is the only Angel Island ferry service with departures from San Francisco; boats leave from Pier 41.