See.. no multi quotes.. its just less pretentious...
this one gives you an idea of what i would like to have
http://www.youtube.com/watch?v=t-WyreE9ZkI
but if you watch it for a while, focus on a single plane, you will notice it makes a pass along the outside, shrinks then passes thru the inside..
its like a tubular tank tread..
BTW this is fun too...
http://en.wikipedia.org/wiki/Impossible_object