Visible from Fisherman's Wharf, Alcatraz Island (aka "The Rock") has seen a checkered history. Juan Manuel Ayala discovered it in 1775 and named it after the many pelicans that nested on the island. From the 1850s to 1933, when the army vacated the island, it served as a military post, protecting the bay's shoreline. In 1934, the government converted the buildings of the military outpost into a maximum-security prison. Given the sheer cliffs, treacherous tides and currents, and frigid water temperatures, it was believed to be a totally escape-proof prison. Among the famous gangsters who occupied cell blocks A through D were Al Capone, Robert Stroud, the so-called Birdman of Alcatraz (because he was an expert in ornithological diseases), Machine Gun Kelly, and Alvin Karpis. It cost a fortune to keep them imprisoned here because all supplies, including water, had to be shipped in. In 1963, after an apparent escape in which no bodies were recovered, the government closed the prison. In 1969, a group of Native Americans chartered a boat to the island to symbolically reclaim the island for the Indian people. They occupied the island until 1971, the longest occupation of a federal facility by Native Americans to this day, when they were forcibly removed by the U.S. government (see www.nps.gov/alcatraz/indian.html for more information on the Native American occupation of Alcatraz). The next year the island became part of the Golden Gate National Recreation Area. The wildlife that was driven away during the military and prison years has begun to return -- the black-crested night heron and other seabirds are nesting here again -- and a new trail passes through the island's nature areas. Tours, including an audio tour of the prison block and a slide show, are given by the park's rangers, who entertain their guests with interesting anecdotes.

Allow about 2 1/2 hours for the round-trip and the tour. Wear comfortable shoes and take a heavy sweater or windbreaker, because even when the sun's out, it's cold. The National Park Service also notes that there are a lot of hills to climb on the tour. The excursion is popular and space is limited, so purchase tickets as far in advance as possible. Blue & Gold Fleet (tel. 415/705-5555; www.blueandgoldfleet.com) operates the tour; they accept American Express, MasterCard, and Visa, and there's a $2.25-per-ticket service charge for phone orders. You can also buy tickets in advance from the Blue & Gold ticket office on Pier 41 or online at www.telesails.com. "Alcatraz After Dark" tours are available Thursday through Sunday. The tour is a more intimate and wonderfully spooky experience, and the proceeds go to restoration and preservation projects. Check the Blue & Gold Fleet website for updated prices and departure times.

For those who want to get a closer look at Alcatraz without going ashore, two boat-tour operators offer short circumnavigations of the island.