Southern Cavern (Japanese: 南の洞穴 Southern Cave) is a dungeon in Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team and Pokémon Mystery Dungeon: Rescue Team DX that contains 50 floors. It is automatically unlocked on obtaining the Boulder Cave Friend Area from an optional rescue mission, after the completion of the main story.
The Metal Coat can be found on 49F and 50F.
In the remakes, the last floor contains 5 Evolution Crystals, 2 Deluxe Boxes, and 1 Focus Blast TM.
Note: The % are rough estimates.