El nacimiento de Venus

Nobody is quite sure what this painting shows. It has long been called the Birth of Venus, but scholars still argue the point. The woman on the shell might be Venus, or the sea-goddess Amphitrite, or the nymph Galatea, and some think the whole scene is really the sea god Neptune leading his watery procession, with no Venus in it at all. Poussin painted it in Rome around 1635 for Cardinal Richelieu, the chief minister of France. From there it travelled a long way. Catherine the Great bought it for the Hermitage in Saint Petersburg, and it hung there until 1932, when the Soviet government, short of cash, sold it abroad. It has been in Philadelphia ever since, its subject still unsettled.