I think that the Alcatraz tour is incredible. The boat ride over gives a beautiful view of the island and of San Francisco. There are options for tours but both times I have gone I choose the cassette tour where you listen on your headset and walk the prison on your own. It is in the words of the actual guards and prisoners and gives you a real feel for what it was like when the island was home to the prison. Such a big part of American history.