When you need it, the room will come and appear as whatever you need at that moment. Just walk in front of the wall a few times and think of what you need the room to be and it will appear.

The DivinationS classroom can be found here, where one can learn about prophecies and tea leaves.

Hidden behind a statue, and protected by various magical spells is the ever mysterious office of the Headmaster of Hogwarts. If you have been called here it could be good or bad.

Located here on the seventh floor is the Gryffindor Common room where only Gryffindors are welcome.