Darkened Stairwell                                     -      N      - 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      -      -

You are standing at the bottom of a winding spiral staircase that climbs
up into dimly-lit space.  Your eyes cannot make out the top of the
staircase, as they are stopped about halfway up when it passes through one
of the lower ceilings, but you are certain it is at least twice as far up as
it looks.  No railing surrounds the elaborate wrought-iron steps, making the
ascension a precarious one.