We were having fun with moebius strips today in physics and I thought I would look up a few more "impossible" objects. Some of them are more well known than others. Most of them were drawn by Escher. Anyway, for your viewing pleasure and mind boggling:

http://www.lewport.wnyric.org/jwanamaker/illusions_plus/images/impossibles/3dring-b.jpg - never ending swirl.

http://www.mathacademy.com/pr/minitext/escher/penrose_triangle.gif - impossible triangle

http://www.scifun.ed.ac.uk/card/images/right/moebius.jpg - moebius strip

http://www.escher.info/images/ILLUSION.jpg - ladders and ropes

http://www.psicologi-psicoterapeuti.it/psychofun/images/escher.jpg - never ending stair

 

Nice. The stairs were clever but the ladders and ropes just gave me a headache.

 

Very sweet. Are these things popular on the internet?
Ropes and ladders one - fantastic.

 

Here's another one - took me quite a while to figure out how this was impossible in the first place:

http://www.world-mysteries.com/illusions/escher_wh.jpg - impossible hoops

 

MC Escher did a lot of art like this. Check out some of his later works.
Edit: Oops, I just realized that you already said that. Well, there's a link to a gallery anyway.
Edit Again: Here's another link, this one shows how different types of illusions work.

 

Wow. Very nice. But this with the ladders was really confusing.

 

Those were pretty cool. Always like seeing things like that.

 

Very fun to look at.

My slaves though... you gave them headaches... that ruins my stock... tsk tsk.

 

Oooh...these are cool.
Yeah, the illusion one...a bit headache inducing. I like the others though, especially the never-ending swirl.

 

Uh, the mobieus strip is possible, just so you know.

 

It's possible in reality, I know, as I've made them before.

However, it is not possibbe in theory: a 2 dimentional shape in a 3 dimentional environment (not including time here).