Impossible Objects wiki (http://en.wikipedia.org/wiki/Impossible_object)
Impossible Objects (http://www.lookmind.com/illusions.php?cat=1&id=1981)
Detail from Belvedere, by Escher
(http://www.panoptikum.net/optischetaeuschungen/cubep_14.gif)
Belvedere, Escher
(http://www.math.technion.ac.il/~rl/M.C.Escher/2/escher-belvedere.gif)
(http://www.geocities.com/CapeCanaveral/Lab/8972/art/impossible5.gif)
Waterfall, by Escher
(http://www.dehora.net/journal/waterfall-escher.jpg)
(http://www.aber.ac.uk/media/Modules/MC10220/Images/legostep.gif)
(http://z.about.com/d/puzzles/1/0/4/S/011.jpg)
(http://haegar.fh-swf.de/spielwiese/unmoeglicheObjekte/bilder/dreieck.jpg)
(http://www.cadfem.com/misc/graphics/cube.gif)
(http://www.simplex.t.u-tokyo.ac.jp/~sugihara/hobby/yuu.jpg)
(http://www.apfel-herz.de/uploads/abilder/Links/optillufiguren.jpg)
(http://media.log-in.ru/i/derevo.jpg)
(http://media.log-in.ru/i/pacifist.gif)
(http://www.mi.sanu.ac.yu/vismath/visbook/orosz/Image1165.jpg)
(http://www.dreamerseye.com/illusions/impossible/stack.gif)
(http://im-possible.info/images/library/grey/g333.gif)
(http://www.veign.com/blog/uploaded_images/1166622255471-745415.jpg)
(http://www.planetperplex.com/img/sys/macdonald_pool.jpg)
(http://www.gerard-siena.it/images/oggetti/quattro0.jpg)
(http://www.csse.uwa.edu.au/awesome/uploads/thumbnail/th_ani.gif)
(http://img151.imageshack.us/img151/2066/parallel6zj.jpg)
(http://www.uvi.edu/SandM/Physics/Opticalillusions/EscherElephant.jpg)
(http://www.imprint.co.uk/C&HK/vol1/vol1-1ps1.gif)
(http://www.lhup.edu/~dsimanek/3d/3dring-b.jpg)