Behind a tapestry at the base of the Astronomy Tower is a door. It's nothing big, nothing fancy, just a little wooden door with a rusted handle that hadn't been opened in many years.
Hayley Harrison, alone, driven by guilt and grief, needed a place that no one knew about. She found the door one day during her Easter Holidays and it has been her room ever since.
It used to be a classroom, once upon a time. There are still desks and chairs, but they were covered in dust when she first found the place. She soon added blankets and pillows to make it a little more cozy, and arranged the desk in such a way as to hide said blankets from immediate view. One wall and most of the cieling is made of windows, offering a view of Hogwarts unrivaled by any other in the school save the roof.
Now the room has three uses. The first, as Hayley's get away. The second, as Otto's hide away. The third, as a place for Hayley and Ela to meet to work on Ela's gifts.