Ulduar on the 3.1 PTR is no secret, so this isn't pictures that are generally seen. This is also a guide how to get to this location on the PTR. Unfortunately you can only get into Ulduar during testing times but someone may still want to try this.
The location of this is past the Yogg-Saron's Prision and through the hallway that looks mechanical with the large tram.
(A LOT OF PICTURES)
Other pictures:
The Open Track
The other side(no tram):
As you can see there's some kind of big red button, probably starting this arena-esque event. The entire room is a door with three openings but when you click the door the entire room moves.