The Perimeter of a Massive Circle                      -      -      - 
(-------------------------------------------------)     W <---(M)---> -
                                                        SW     S      -

While this massive room is probably no more than a hundred feet across,
the curving walls and floor are made of black obsidian, which creates an
illusion of even greater distance.  The high arched ceiling appears to be
made of a material similar to the walls.  Towards the center of the room you
see a crystal gateway atop a large dais.