Château de Chambord, France

Château de Chambord, built between 1519 and 1547 as a hunting lodge for King Francis I, is the largest of the Loire châteaux and a masterpiece of French Renaissance architecture. Its iconic double-helix staircase, thought to be designed by Leonardo da Vinci, allows two people to ascend and descend without meeting. The château spans 5,440 hectares, with 440 rooms, 365 fireplaces, and 84 staircases.