It's safe to say that this is the most important toilet in art history. It was from this second-hand potty that conceptual art in which the concept behind the work takes precedence over the thing itself was born. Marcel Duchamp's 1917 urinal was one of the pieces he referred to as "readymades" art produced from already existing objects. The final product has been likened to the veiled head of a classic Renaissance Madonna and to a seated Buddha. Who says a toilet can't be beautiful?