Standing Beside A Pit                                  -      -      - 
(-------------------------------------------------)     W <---(M)---> -
                                                        -      -      -

At this point the tunnel you have been following comes to an end. 
However, there is a large pit leading down into the darkness below.  The
east wall of the tunnel is is worn and cracked, and although you will have
to leap across the pit to grab hold, you should be able to climb down
safely.