Olympus Coliseum is one of the smallest worlds. Once on the world you enter through the Coliseum Gates. From there you would want to enter the Coliseum: Lobby where you register for Tournaments , and The Coliseum itself, where you competes against, Other fighters. This is where the Keyblade Wielders will be have their tournaments. The Underworld run by the Greek God Hades is also on this world. Only the strongest of fighters know how to enter, and are powerful enough to get out. It is also home to the Underdome.The Underdome or the Underworld Coliseum, is were the strongest fighters who've every lived go to compete, dead or alive. This is were everyone of the Keyblade Master Level and higher will have their Tournaments.