A Tunnels End                                          -      -     NE 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      -      -

You have traveled to the end of the tunnel above the stream, ahead of
you is a small chasm, that doesn't seem to be too deep, and seems possible
to climb down.  The darkness below, though, suggest that there must be
something there that wants to stay hidden, and away from all other life.