The Forbidden Corridor is aptly named. It's guarded by a locked door and it is not wise to unlock to see what is behind it. Or at least it didn't use to be. It used to be home to a giant 3 headed dog named Fluffy who was guarding a trap door that led to where the Sorcerer's Stone was kept. However, after the stone was destroyed, Fluffy was moved into the Forest where he likes to play and romp around. The room he used to guard is empty and there is no sign of the trap door, it's an ideal place to hide from Filch now if one does not want to be caught out of bed and wandering the castle.
