Trapped

Alcatraz was a island in the San Fransisco bay that for a long time was used as a "super prison" because of the governments belief that you could not escape from it before its prison time it was used as a fort to protect the bay. Figuratively speaking it was a pretty tough rock, with the harsh tides, cold water, steep cliffs, and dangerous currents. However due to high cost (EVERYTHING had to be brought to the island by boat) and an attempted escape the prison was shut down in 1963.