Tunnel                                                 -      N      - 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      S      -

This tunnel looks like it is not naturally made.  The walls are very
smooth and the tunnel is almost the same diameter throughout.  The tunnel
provides an escape from the fierce heat of the lava flow.  To the north the
flames and heat of the lava flow scorches the nearby rocks.  This tunnel
provides a safe place to heal wounds from the fire.