Underground Ruins

Underground Ruins is an area located within Clay Road, where Regirock, Regice, and Registeel can be caught. Their method of capture depends on the game version; Regirock is found in the Rock Peak Room after a puzzle is solved, while Regice is found with the Iceberg Key in Pokémon White Version 2 and Registeel with the Iron Key in Pokémon Black Version 2. The key unavailable in one game version can be transferred via the Unova Link.

If all three Pokémon are caught here, Regigigas can be captured in Twist Mountain.