The Cave of Monsters

Like the Pit of the 100 Trials, it does have monsters.

Bub and Bob (or Bubblun and Bobblun for japanese) went there before to defeat monsters in order to make their way through to save their girlfriends from the clutches of Grumple Gromit (or Drunk for japanese.)

These are the following monsters they live:
Bubble Buster
Beluga
Stoner
Hullaballoon
Coiley
Incendo
Willy Whistle (Mini-Drunk)
Super Socket
Baron von Blubba
Rubblen
Bubble Dragon Ghost