http://www.panoptikum.net/optischetaeuschungen/opticalillusions.htm

http://www.anc.ed.ac.uk/~amos/visualillusion.html

http://www.click2amuse.com/fun/optical/

http://www.geocities.com/blondielinks/illusion3.html

http://www.sandlotscience.com/

http://hoteloverlook.com/page_5.html