You must have the building, but not even connected to a road...The description says that Alcatraz creates four units "that you could produce in your city". Does that mean you only have to have developed the technology, or that you also have to have the military building too?
My view......this is a crucial GB....Thanks. Considering it's size it really only seems worth it if you are planning on doing a ton of fighting. I think I will skip building this one.