A Warm Tunnel                                          -      N      - 
(-------------------------------------------------)     W <---(M)---> -
                                                        -      -      -

This relatively wide passageway is also much hotter than the chambers
nearby.  You can see a hole in the ceiling next to the south wall, but it is
a bit too high for you to reach.  The tunnel leads north from here, but
there is also a dim red glow coming from a hole in the west wall.