Mistralton Cave is a cave located on Route 6 in the western half of the Unova region. It can be accessed by using Surf from Route 6; in Pokémon Black 2 and White 2, Mistralton Cave can also be accessed via the Clay Tunnel's western terminus. Flash is needed to fully illuminate the cave.
In Pokémon Black and White, the Guidance Chamber, home of the Legendary Pokémon Cobalion, is located here. After encountering it, the player will be able to access Terrakion in Victory Road and Virizion in Pinwheel Forest.