The Dancing Lady is a fine optical illusion: she moves both clockwise and counterclockwise, depending on how your brain views her.
Blink once or twice, and you can change her direction. However, most people have an innate tendency to see her moving in one or the other.
People's Cube uses this image as the basis for a discussion about the subjectivity of perception.
Unfiltered, unprocessed perception isn't truth, but we already know that.