Got my handcrafted glass 2-manifold from Clifford Stoll recently. It's a bottle which outside is it's inside, and it has 0 volume (well, at least in it's usual habitat (4 spatial dimensions) and not immersed into our 3 spatial dimensions..) See: http://en.wikipedia.org/wiki/Klein_bottle Here it is, in a dark room, illuminated by a blue LED:
And here is the crazy guy who makes them:
If you haven't seen it before, you should check out his TED talk.