Koopatraz State Prison

Koopatraz State Prison, usually just referred to simply as Koopatraz, is a maximum security penitentiary situated on a small island in Trouter Bay. Until its demise, Koopatraz State Prison was owned and operated by Warden Koopa, and used as a dungeon to house many of his own prisoners. Bailiff Mouser also served as Koopatraz's second-in-command. Surrounded by large walls and a water tower, the prison contained cell blocks for both male and female prisoners, in addition to solitary cells. Other known rooms included a mess hall, a laundry room, and sleeping quarters for its staff. It is based on the real world, a famous jail off the coast of San Francisco, California.

Although many prisoners used to live in Koopatraz State Prison, most of them had died by the time it sank beneath Trouter Bay. Known punishments forced upon the prisoners included meals consisting of bread, water, and Koopa Surprise, breaking rocks and laundry duty.

History
Mario, Luigi, Princess Toadstool, and Toad are captured by King Koopa, and eventually put on trial before him, while he poses as the judge. Regardless of their actions, Judge Koopa makes up lies, and sentenced them all to serve five-hundred years at Koopatraz State Prison. Upon arriving, they are greeted by Warden Koopa, who becomes their cruel warden because he has fun being their crooked judge. Mario, Luigi, and Toad are assigned to share a cell with Gramps, Koopatraz's only other living prisoner, while Princess Toadstool is placed in her own cell.

After Toad reunites with Gramps, Luigi comes up with an escape plan that involves digging under the prison to reach the other side of the front gate, where they could escape on a boat. In order to steal the forks necessary for the job, Mario starts a food fight in the mess hall, which results in Warden Koopa revoking their future meals. Using forks they stole, the male prisoners dig a tunnel, but accidentally surface in Warden Koopa's bedroom, greatly angering him. As a result, he extends their sentence and assigns them to hard labor.

Mario steals a block of soap during laundry duty, and whittles a phony Bob-Omb from it, which he uses to scare a Goomba guard, whose keys he steals. Mario uses the keys to rescue the rest of the prisoners, and they escape from Warden Koopa by jumping into a sewer drain, which leads them to a cavern with a large drain stopper. The group pulls out the drain stopper, and surfaces next to the island, where they escape on a boat, while the island begins to flood. Warden Koopa attempts to thwart their escape with a Bob-Omb, but it fails, and soon the entire island of Koopatraz State Prison sinks beneath Trouter Bay.