Humid Tunnel                                           -      N      - 
(-------------------------------------------------)     W <---(M)---> -
                                                        -      -      -

This tunnel is quite small, and you are forced to stoop down in order to
walk through it.  The air is heavy with moisture, making it rather hard to
breathe.  The tunnel runs off into darkness to the north, and there is a
small hole in the west wall through which you can see a cavern.