The Poseidome Colosseum is the Colosseum of Atlantis. It first appears in the episode "Neptune's Spatula" and is the main setting of the first boss level in the video games Battle for Bikini Bottom and Battle for Bikini Bottom - Rehydrated.
It is a large concrete, Greek building, with large concrete cylinders at the main entrance. Inside there is a modern arena, with show lights, a ring, and many rows of viewing seats.
Role in series
King Neptune and SpongeBob have a cooking contest in this building.
Battle for Bikini Bottom/Battle for Bikini Bottom - Rehydrated
It is the main setting of the first boss level, where Robo-Sandy is the boss and the player must defeat her as SpongeBob and Patrick.
It is one of the arenas.