Musée de l'Ermitage

Most of the Hermitage sits inside the Winter Palace, the green-and-white Baroque residence of the Russian tsars on the bank of the Neva in Saint Petersburg. The collection began there as a private pleasure. In 1764 Empress Catherine the Great took 225 Dutch and Flemish paintings that a Berlin merchant, Johann Gotzkowsky, had gathered for the king of Prussia, who, broke after a long war, never paid for them. Catherine did, and hung them in rooms so private she called them her hermitage, a retreat where almost no one was allowed in.

Two and a half centuries of buying later, it is one of the largest art collections in the world. You climb the Jordan Staircase under gold and mirrors and work toward the paintings people come for: Rembrandt's Return of the Prodigal Son, the old father's hands resting on his ragged son's back, and two small Madonnas by Leonardo da Vinci, the Benois and the Litta, painted when he was young. In one room a life-size Peacock Clock, an 18th-century English automaton, still spreads its gilded tail when it is wound.

The building has been through a lot. A fire gutted the palace in 1837, the 1917 revolution swept the last tsar out of these rooms, and when German forces besieged Leningrad in 1941 the staff crated up more than a million objects and shipped them east to the Urals, leaving the empty frames hanging on the walls. Guides gave tours of those bare frames through the siege. The works came back when it ended, and the cats kept in the cellars to hunt rats, a tradition going back to Catherine's day, are still on the payroll.