Disappearing-step staircase

"[...] some with a vanishing step halfway up that you had to remember to jump."

- The stairs.

These enchanted stairs are staircases (or spiral staircases) in Hogwarts that remove a step halfway up, so you had to remember to jump. They were most likely developed by Rowena Ravenclaw, as she knows most about magic.

Appearances

 * Harry Potter and the Philosopher's Stone