Room of Requirement

The Room of Requirement used to be a place to hide when you were running from Filch, or hide something away, or even use it as a bathroom! 200 years and the Fiendfyre haven't been kind to it, and now a days it's only used as the Resistance's base. Unlike in it's previous glory, the only room it can provide is the Room of Hidden Things, however, almost anything that was in the room at the time of the Fiendfyre was desrtroyed or burned to ash. It can still hide itself in times of need, but now only the Resistance can get in with a special charm they placed on the door.