[N8 v2.0]

Möbius Strip

This is something you can make that actually only has one side...

Linky: http://www.cut-the-knot.org/do_you_know/moebius.shtml

 

[Wingnut]

Escher has a lot of art that makes you think twice.

On the topic of brain teasers: If you try and fail, and succeed, then which did you do?

 

[stuntmatty]

Does killing time damage eternity?