indoor aquarium .

This is definitely one of the creepiest places in the whole castle. If you stumble up the tank, which appears to be just a window into blackness, unless the lights are on, until a huge white eye forms out of nowhere and a huge black shape drifts by. Completely terrifying, I'd say. It's an unpleasant place, out of class, because the teacher's not there to illuminate the water or de-humidify the air, and if you try to do these yourself... Well, good luck with that.