What's the deal with the library off the clock tower?

Question

Off the clock tower there's a screen with a big official-looking building. When you go inside there's a smallish room with some pictures on the wall, a bookshelf, and a fireplace.

I've tried pressing up in front of the fireplace, but nothing happens. According to the map there's a secret in this room, but for the life of me I don't see any clues there.

Answer 1

Press X next to the bookshelf—it's a false door.

Answer 2

Press X in front of the bookshelf and rotate. I went right by it the first time, too.