Alcatraz: The Rock

This is actually the photo of a National Park. Confused? Don't be. This is a photo of Alcatrza, called 'The Rock', a small island located in the middle of San Francisco Bay. It is pretty famous also by the name of a movie with the same name, starring Sean Connery and Nicholas Cage.
The island has a chequered history, finally culimnating in being a federal prison till 1963, when it was freed and made a national park. It is a popular tourist destination, reachable by a ferry ride from Fisherman's Wharf.
It was a natural prison, since it was not easily accessible, had freezing waters that deterred most people trying to escape. Some of the most famous prisoners over there were Al Capone and George 'Machine Gun' Kelly.