Alcatraz is part of the Golden Gate National Recreation Area, including Muir Woods and the Golden Gate Bridge. (Photos by Carla Babb and Ryan Newell)

The prison greeted approaching ships with a threat: "Persons procuring or concealing escape of prisoners are subject to prosecution and imprisonment."

The Rock sits about 2.5 kilometers away from San Francisco. Part of the Rock is closed each year from February to September for bird breeding season.

Before it was a prison, Alcatraz was known for housing the first lighthouse and US-built fort on the West Coast to protect San Francisco during the gold rush.

Alcatraz prison housed 300 cells. 

Recreating cells ready for new inmates on Alcatraz.

Tourists can weave in and out of cells guided by an audio tour told by the actual voices of former inmates, guards and others that lived on the island.

Robert Stroud, better known as the Birdman of Alcatraz, was so unruly the guards moved him out of the cellhouse to this isolation cell in the hospital wing.

Stroud spent his last six years on the island in this room.

Three inmates used spoons to chisel through the brick wall of their cell during the escape of June 1962. They placed paper mached heads on their beds and fake air vent covers to keep the guards from discovering the holes.

Every turn at Alcatraz reveals layers of its history; the 8-foot-thick wall in the forefront is part of the fort built in the 1800's, and the prison cell house walls to the left.

The warden's quarters at Alcatraz, which burned in a fire during the American Indian occupation in 1970.

Knives in the kitchen cupboards were outlined in black so prison guards could easily see if one ever went missing.

Prisoners were allowed scheduled visits once per month. Visitors had to sit outside the cellhouse and talk through glass panes.

About 5,000 visit Alcatraz each day.