Then there were doors that wouldn't open unless you asked politely,or tickled them in exactly the right place, and doors that weren't really doors at all, but solid walls just pretending.
It was very hard to remember where anything was because it all seemed to move around a lot. The people in the portraits kept going to visit each other and Harry was sure the coats of armour could walk.
The ghosts didn't help, either. It was always a nasty shock when one of them glided suddenly through a door you were trying to open.