The Underwhere is an area in Super Paper Mario. It is the seventh area in the game.
7-1 is the first level of The Underwhere. It is a spoof of The Underworld. It is where Luigi is unlocked as a playable character, and where Luvbi is introduced.
7-2 is the second level of The Underwhere. It is where Bowser is fought, and then unlocked again. It is also where the Three Hags were introduced, and where The Underchomp was fought.
7-3 is the third level in The Underwhere. It is set in The Overthere, and has several mythology references. It is where Princess Peach is unlocked again.
7-4 is the fourth level of The Underwhere. It is set in The Overthere. It is where Bonechill is fought. After he is defeated, Mario and Co. get the seventh Pure Heart.