Escher lizard paving-stones

GeckoStone makes tesselated paving stones that look like Escher's interlocking lizards. (hilariously, they've registered a trademark and claim copyright on this work derived from a classic Escher work that is, itself, copyrighted -- and there's no evidence that they licensed the design from Escher's estate; every pirate wants to be an admiral!)

GeckoStone (via Make)