It was fascinating.
You have to take a ferry to get there, which pays for your admission into the park, along with a great audio tour.
Once we got on the island, we started the audio tour. The tour was great - It has you walk throughout the cell house, takes you to different cells, and gives you a real sense of the history of Alcatraz. It lasts about an hour, but we took our time, stopping and exploring parts that the tour went by quickly. There was a lot to take in. It was my first time ever visiting a prison, and it made me really curious as to what prisons look like on the inside these days (apart from my expectations from Orange is the New Black).
The other perk of Alcatraz is the amazing views from every spot on the island. Each gives you a perfect bay background, no matter which direction you face!