Negative sculpture
Is the sculpture a depression or does it protrude? Light and darkness can be reinterpreted so that your brain sees it as a normal three-dimensional sculpture.
The sculpture depicts the Egyptian pharaoh Ramses and is actually an indentation (a negative sculpture). With the right illumination and when viewed from the distance, however, we see it as standing out from the surface (a positive sculpture). If you move sideways, the figure appears to follow you by turning its head.