Koopaseum

The Koopaseum is a large, Colosseum-like structure in the middle of the Gritzy Desert that appears in Mario & Luigi: Partners in Time. In the past, the Mario brothers and the Baby Mario brothers came to the Koopaseum looking for Princess Peach. Once the brothers entered, they saw Peach being eaten by Petey Piranha, by Princess Shroob's commands.

In the Koopaseum, the brothers fight Shrooboid Brat in the middle of a stage with millions of Shroobs watching them. Even though the brothers defeat Shrooboid Brat, the brothers are taken down by lots of Shroobswith hammers. The adult and baby Mario brothers are then dropped to Gritzy Caves, which is right below the museum.

It is unknown who really owns the museum but because of the name of the museum, it is very possible that the Koopas once owned the museum but Shroobs later took over it. It is also possible that when the Shroobs came to Gritzy Desert, the Koopaseum was already abandoned.