Play an out-of-tune piano, tilt back the head of a statue or slide the right volume out of a bookcase and you may gain entrance to the Batcave, or some other hidden space within an eccentric billionaire’s mansion. There are plenty of examples in fiction of locations or facilities hidden from sight, or designed to be accessible (or even simply known) only to one or a few people. What is your favorite example of such a secret place in a fictional story?

Bonus: The least-credibly-hidden secret place in a movie or show?

Game Bonus: If you are a gamer, what has been the most challenging hidden room or level to find or access, in your experience? Did you find it accidentally, or were you aware beforehand of its existence?