Room of Requirements

The Room of Requirement is a room that can only be discovered by those who are in need of it and is often called the "Come and Go Room" by the house elves. It is located on the wall opposite of the tapestry of Barnabas the Barmy trying to teach trolls to dance ballet. To get it to appear you must pace back and forth 3 times in front of the blank wall and concentrate hard and what is needed.