Which direction are this boy and girl facing?
The girl is standing on her head...
or arching her back underneath the boy.
The boy is standing on his head...
or arching his back on top of the girl.
For a two-dimensional version of this optical illusion, see: Two deceptive 19th Century puzzles: The Trick Mule Puzzle, and The Dead Dog Puzzle, Deceptology>>
Chinese Optical Illusion Antique Bronze Boy Girl Statue Sculpture Figurine, Tremblu>>