The Unknown Dungeon (Japanese: ななしの洞窟Nameless Cave) is a very small cave in southern Kalos that can be accessed from Pokémon Village. A sole Mewtwo resides in the center with a game-specific Mewtwonite. The Unknown Dungeon is only accessible to Trainers who enter the Hall of Fame. Surf is needed to access the cave.
Its purpose as a place to catch Mewtwo is a direct reference to Cerulean Cave in Kanto. It also shares its name with the alternative moniker for Cerulean Cave used in Japanese releases of the Generation I games.
The Unknown Dungeon is a tiny cave whose entrance is found in the side of a mountain. The cave is barren in terms of terrain aside from the occasional water drop and the few rocks that dot the floor. Mewtwo awaits the player in the center of the cave, facing away from the entrance.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
