Sander Wit has posted an wonderful image on Elysiun that is based on the work 'Up and Down' by the Dutch artist M.C. Escher.
I really like Escher's works and I have stared at this one for a long time and tried to figure out how he did it. It didn't help; my only hope now it to lure Sander into writing a 'howto'. If I succeed you'll read about it later, of course.
The full-size image is posted on Elysiun.