A Warm Tunnel                                          -      -     NE 
(-------------------------------------------------)     - <---(M)---> -
                                                        SW     -      -

This relatively wide passageway is also much hotter than the chambers
nearby.  You can see that there are a number of holes in the ceiling and
high on the walls, although the look like they were formed naturally.  An
occasional gust of steam shoots from one of the holes, suggesting that there
is some kind of volcanic activity taking place nearby.