A Band on Sanity
This animation of an impossible ribbon was created by Erwin Bonsma. Depending on how you look at it, this ribbon can be perceived as rotating in two different ways. He credits the original idea to M.C. Escher’s print titled “Cube with Magic Ribbons” which happens to be the first drawing by Escher to feature a truly impossible object.
(via Erwin Bonsma)