What spiral staircase design is associated with Leonardo da Vinci at Château de Chambord?

The staircase associated with Leonardo da Vinci at Château de Chambord is a double-helix staircase.

Chambord’s central staircase contains two spiral flights that wind around one another without meeting. A person can ascend one flight while another person uses the other, and the two paths provide views through the open central space. The arrangement is one of the château’s most recognizable architectural features.

Leonardo spent the last years of his life in France under the patronage of King Francis I, who commissioned Chambord. Leonardo is widely associated with the staircase’s concept, but historians debate how much of the finished château he directly designed. The building was constructed after his death, beginning in 1519.

The staircase is often called a double helix, not a double spiral in the strict mathematical sense. The two intertwined paths are the key identifying feature.