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

This relatively wide passageway is also much hotter than the chambers
nearby.  The tunnel comes to an abrubt end here, but there is a large hole
next to the north wall.  You can see another tunnel directly below, and it
should be safe to drop down.  However, you may have to find another way to
get back up.