The Meeting Room is in the 3rd Dimension, but is in an incorporeal, separate part of it, outside of the mainstream timelines, and yet connected to the True Timeline.
The Meeting Room is a large, all black room, with its only furnishings being a large, glowing black and white table with an image of all the continents of the Earth on it. Around it, the Watcher Meeting members sit in a circle. In the back parts of the room, a Warden stands guard. The Meeting Room is only physical when the player arrives. When they leave, it returns to its incorporeal state, where a lot of the aspects of reality no longer exist.