"The Weasley trick does it again!"
Ronald Weasley after opening one of these doors in the Marauder's Map chamber

These doors are doors which pretend to be walls. They are scattered all across Hogwarts School of Witchcraft and Wizardry, from hidden chambers far underground to public hang-out spots in the middle of a corridor. Ronald Weasley is able to open these doors.

They were possibly developed in the castle by Rowena Ravenclaw, as she knew most of the magic in the school. Chests were able to be found in most of them, but in some challenge chambers there were pixies in some.