On an island in San Francisco's bay sits...
Alcatraz prison. 'The Rock'.
The only way on and off the island is by boat - unless you want to mess with some serious currents and apparently potential sharks. Not the best situation to be in...The prison has 'hosted' some infamous names such as Al Capone! and we had a brilliant audio guide round the place with true stories of the inmates (including the famous 1962 attempted escape) to go with it.
View of San Francisco from one of the cells - frustrating to say the least!
The prison is clearly closed now - a landmark site instead. It's well worth a visit, and personally I enjoyed the grounds and views just as much as the stories and prison itself.