The Colosseum is a Second Sea location found in Kingdom of Rose, just to the left of Don Swan's Mansion. It is an important area for both PvP and progression, serving as the home of the integrated Friendly 1v1 system and playing a major role in the Colosseum Quest.

The Colosseum is also notable because the Legendary Sword Dealer can spawn in one of its northeastern arches, making it a location that many sword collectors regularly check.

Structurally, the arena has a circular design surrounded by water, with four small bridges connecting the central arena to its entrances and exits. The area has no roof, giving it a wide open layout suited for duels and movement-heavy fights.