Isometric illusion

A photograph of a three-dimensional installation showing the logo of science center Heureka. The logo can be viewed in two different ways; with the cubes appearing to be pushed outward, or, as it in reality is, the cubes pushed inward.

An isometric projection forming a cube/box within cruciform walls/floors, this design is incorporated in a crop circle.

An isometric illusion (also called an ambiguous figure or inside/outside illusion) is a type of optical illusion, specifically one due to multistable perception. In general, any shape built entirely of same-length (i.e., isometric) lines that does not clearly indicate relative direction between its components will evoke such a perceptual "flip-flopping".

The Necker Cube is a famous example of an isometric illusion.