Under Colosseum (Japanese: アンダーコロシアムUnder Colosseum) is a location in Orre. In Pokémon Colosseum is located in the northern part of The Under, reachable only by obtaining a UFO F-Disk. The Under Colosseum is not present in Pokémon XD: Gale of Darkness due to The Under no longer existing.
The Under Colosseum is a gigantic arena with chains dangling from the roof and hundreds of lights. It shows many Japanese neon signs and icons on the walls, much like The Under does itself. The spectators may watch the ongoing battles in different floor levels that have metal fences that block most of the openings to avoid anyone from moving in on the match.
Pokémon Colosseum
Cipher AdminVenus once used the Colosseum to distribute Shadow Pokémon to Trainers who won knockout challenges, just as Miror B. did in Pyrite Town. Once Wes defeats Venus and she flees, the Colosseum resumes normal operation, offering cash and TM prizes rather than Shadow Pokémon.