This post was published more than a few years ago (on 2004-05-21) and may contain inaccurate technical information, outmoded thoughts, or cringe takes. Proceed at your own risk.
AAl just sent me this link to Escher's "Relativity" in LEGO. A pretty amazing feat of LEGO engineering, with links to a few other Escher drawings that the author has built with LEGO blocks. The extended construction photos are quite amazing.