here's the website of a guy who has way too much time and too many Lego bricks at his disposal, so he recreates MC Escher's "impossible" architectures in Lego, the latest one being "Relativity" :

http://www.andrewlipson.com/escher/relativity.html

My favourite is Ascending / Descending:

http://www.andrewlipson.com/escher/ascending.html

Not only is it seriously mindboggling and hilariously funny at the same time, it also helped me understand the original picture.