Alcatraz is the name of a high security prison in the world of the Wild Arms: Twilight Venom anime, overseen by Warden Kihano. The entire structure is actually floating in the air; it is orbiting around a large cone-shaped groove in the ground that has walls lined with magnetic rock that attract it. It takes one full year for Alcatraz to complete it's orbit around the crater; ships leaving and entering Alcatraz also only come around once a year. Due to the fact that the transport ships only come once a year and that there's nothing but sky above and rock below the rest of the year Alcatraz has gained a reputation for being an inescapable prison. It is also sometimes used to store top-secret and potentially dangerous weapons or items. The prison also has a dragon-like monster known as a Falconvein that can be used in battle against escaped convicts. The warden also has permission to execute the death penalty on prisoners in extreme situations.
The prison of Alcatraz is where the majority of the sereis' first episode, Sleeping Dirty, takes place. It is also the location at which the main heroes, minus Issac, all meet up for the first time. Dr. Kiel Aronnax had gone to the island to make a deal with the warden and whatever organization it represented but soon found himself hanging upside down being tortured. Sheyenne Rainstorm's mind and fake child-body were both being stored in a vault inside Alcatraz. Loretta Oratorio, Mirabelle Graceland, and Jerusha broke into the prison on their hot air ballon with the aid of Loretta's magical cards which cast a spell when thrown. They end up rescuing Dr. Aronnax and are disappointed to find that the treasure they were hunting for was actually Sheyenne. By the end of the episode they are also stranded on the island for an unspecified length of time.
The prison of Alcatraz is named after the Island of Alcatraz, just off the coast of California Bay. As opposed to be flying in the sky it is an isolated island surrounded by water. For a long time there was a military prison for the United States operating on the island, later becoming classified as a federal prison and now functing as a famous tourist attraction.