here's link to an NPR article about a famous optical illusion exhibition: http://thin.npr.org/s.php?sId=162790780&rid=5 . I didnt really know in which category this belonged....
Talk of the Nation, October 12, 2012 · Artist Julian Hoeber's "Demon Hill," now on view at the Harris Lieberman Gallery in New York City, is modelled after a roadside attraction called a "gravitational mystery spot" — where water runs uphill and gravity doesn't behave as expected. Science Friday talked to cognitive scientist Michael Landy about what happens to our perceptual system inside the exhibition.