Which French Renaissance château features a famous double-helix staircase?

The French Renaissance château famous for its double-helix staircase is Château de Chambord.

Located in France’s Loire Valley, Chambord was commissioned by King Francis I, with construction beginning in 1519. Its central keep is arranged around a remarkable staircase made of two intertwined flights. People can ascend simultaneously while seeing one another through openings, yet the two routes never meet.

The staircase rises through the château’s three main floors and continues toward the roof terrace, beneath a lantern tower. It is often credited to Leonardo da Vinci, who lived near Francis I’s court, but historians have not definitively proved that he designed it. The château’s overall design is also associated with Domenico da Cortona and other architects.

Chambord is sometimes confused with Chenonceau or Azay-le-Rideau, other celebrated Loire châteaux. Its double-helix staircase, however, is the signature feature that most clearly identifies Chambord.