Delicious! Found via http://thesilverliningblog.com/2010/01/05/fontana-modern-masters/
More at http://fontanamodernmasters.org/
How 1960s Op Art and cut-up culture informed the cover designs of Fontana Modern Masters in the 1970s http://www.eyemagazine.com/feature.php?id=170&fid=777
My eyes, my eyes! These are just the tip of the iceberg, from the excellent site by Michael Bach - http://www.michaelbach.de/ot/index.html
"Stare at the centre of the figure for a while. Some ‘scintillating’ activity will build up in the violet and blue annuli. Some observers also report a circular rotation within these regions; things will begin to “run around in circles”. This image “The Enigma” is by Isia Leviant (1981), Palais de la Découverte, Paris."
Rotating Snake Illusion
Source: http://www.michaelbach.de/ot/mot_rotsnake/index.html and http://www.ritsumei.ac.jp/~akitaoka/rotsnake.gif
"Rotation of adequate figures creates a three-dimensional illusion. It can take some time until the percept emerges. In the example on the right, envisaging a rotating crater may help. The kinetic depth effect (KDE) is a similar related phenomenon." Source: http://www.michaelbach.de/ot/mot_ske/index.html#