A Wavering Tunnel                                      -      -      - 
(-------------------------------------------------)     W <---(M)---> E
                                                        -      -      -

This passage is unlike anything you've ever seen before, but it somehow
seems vaguely familiar at the same time.  When you look at the walls they
seem solid and stable, but if you don't focus on anything in particular the
entire area becomes almost intangible, as if your attention is all that is
making it real.