Reality or something other?

"It has happened to me, while taking solitary walks through the woods of Baarn that I would suddenly stop in my tracks and stand stiff as a board, overcome by a frightening, unreal and yet blissful sense of standing eye-to-eye with the inexplicable.  The tree there in front of me, as an object, as part of the woods, is perhaps not so amazing, but the space between it and me, suddenly seems unfathomable.

He who wants to depict something nonexistent has to follow certain rules.  Those rules are more or less the same as for fairy tales.

The element of the inscrutable, on which he now wants to focus attention, needs to be surrounded, to be veiled by a perfectly common everyday evidence, recognisable to all.  That true-to-nature environment, acceptable to any superficial spectator, is indispensable for creating the desired shock."

M.C.Escher in his lecture, 
"The Impossible". 1963