Altering Cave is a cave found in FireRed, LeafGreen, Emerald, Diamond, Pearl, and Platinum. In FireRed and LeafGreen, Altering Cave is on Island 6. In Emerald it is located on Route 103 on the Mauville side. You can only access Altering Cave after you beat the Elite Four, and it only has Zubat in it. The Pokemon in the cave change.