Which unique item would you find in the Château de Chambord, France?

The unique feature of Chambord is a double helix staircase. Set in the central axis of the castle it was a revolutionary design and an engineering masterpiece. Conceived by Leonardo da Vinci, the ingenious spiral open staircase joins various levels via two sets of steps set in a huge lantern-like case. People can ascend on one side without meeting or making eye contact with those who are descending on the other side. Listed as a UNESCO (The United Nations Educational, Scientific and Cultural Organization) World Heritage Site in 1981, the Château de Chambord has been home to many illustrious guests over the centuries. Louis XIV completed the work of constructing the castle.

François I (12 September 1494 – 31 March 1547) was King of France from 1515 until his death in 1547. On his victorious return from the Battle of Marignan in 1515, he decided to build the Château de Chambord in the valley of the River Loire, about an hour from Paris.

A prodigious patron of the arts, he initiated the French Renaissance by attracting many Italian artists to work on the Château de Chambord including Leonardo da Vinci, who brought the Mona Lisa with him, which François had acquired. Chambord is a symbol of the French Renaissance and of the power of a passionate ruler who revered the arts. Despite this, Francois spent only 50 days there.

Notwithstanding the extraordinary renown of Chambord, the identity of its architect has remained an enigma.