The ghosts of Al Capone, George “Machine Gun” Kelly and Alvin “Creepy” Karpis still stalk the abandoned corridors of one of the world’s bleakest and toughest prisons. But since the maximum security facility closed in 1963, Alcatraz Island has been welcoming “guests” of a different kind. This rocky outcrop in San Francisco Bay is now a National Park, with thousands of people every year making the short ferry ride across the channel that separated the most notorious criminals of their day from the bright lights of the city.

Alcatraz’s fortress-like walls and isolated location were considered impregnable. Between 1934 and 1963 it was the last resort for especially dangerous and disruptive prisoners, many in solitary confinement awaiting the death penalty or serving out life sentences for murder and violent robbery. Some attempted escape, only to be recaptured or, in a few cases, shot by marksmen or swept away by the treacherous currents of the bay. It was claimed that no prisoner ever succeeded in getting away from Alcatraz alive, although the fate of the three who made a daring bid for freedom in 1962 on a life raft made from prison-issue raincoats remains unknown to this day.

Tours of “the Rock”, as it’s commonly known, take in the grim cell blocks and walled exercise yard of the former penitentiary. Join a tour group or plan your own route with the help of an audio guide, included in the ferry round trip. Visitors are at liberty to explore the rest of the island, which also boasts the first lighthouse on the American West Coast, with origins dating from 1854, and enjoy views of the mainland uninterrupted by prison bars.

Ferries depart from Pier 33 at the Embarcadero and the crossing takes around 15 minutes. It’s easy to lose track of time wandering around this atmospheric place contemplating its strange history and admiring the flora and fauna that have made the Rock their home, so remember to check the departure of the last ferry back to the mainland, usually around 4.25 p.m. The ferries get particularly busy in summer at the peak of the tourist season, so it’s worth buying your tickets in advance to beat the queues.