The Penrose Triangle looks like an impossible solid (see this). It formed the basis of some of the more famous drawings by M.C. Escher.
My previous snow stomp art:
The Penrose Triangle (this post)
Snowflakes (done with my granddaughters)
Diagonally Warped in a Parallel Universe, Part 2
Diagonally Warped in a Parallel Universe
A weak pattern in the blowing snow.