Olympus Coliseum from KH
Olympus Coliseum is featured in Kingdom Hearts and returns in Kingdom Hearts II. It is based on Disney's thirty-fifth animated feature, Hercules. The Coliseum is protected by the might of Hercules and antagonized by the wily Hades. Sora trains here and can compete in various tournaments.
Olympus Coliseum is rather sparse in Kingdom Hearts, consisting of only the main entrance, a lobby and the coliseum itself. In Kingdom Hearts II, Hades opens a portal to the Underworld near the exit of the Coliseum. The Underworld consists of its own "lobby" which is one boat ride across the river Styx to the Underdrome, the Underworld's equivalent to the Coliseum, the Lost Road to the Lock and the Cave of the Dead which leads to Hades' Chamber. All of these Underworld areas are infested with Heartless, as well as mysterious white puffs of smoke.