The unsolved mystery of France's iconic Loire Valley

Five hundred years on, the architect of this famous French castle remains a mystery. Could it be Leonardo da Vinci?

• By Adrienne Bernhard

17 March 2020

‪Last year‪ marked the 500th anniversary of Leonardo da Vinci’s death in Amboise, a town on the southern bank of the Loire River in France. In 1519, that very same year, construction began on a castle 50km east of Amboise, the Château de Chambord – the largest castle in the Loire Valley and widely considered one of the most impressive examples of French Renaissance and Medieval Revival architecture.
But whoever originally imagined the defining features of this great monument remains a mystery: Chambord was commissioned by King Francis I, but no architectural plan for it exists.

Some art historians think the clue to the castle’s design may lie in Chambord’s most iconic feature: its unusual “double helix staircase”, which allows two people to ascend without ever having to cross paths (perfect for steering clear of servants or irritating relatives). Composed of two helical ramps that twist like a strand of DNA around a hollow core, the staircase services the main floors of the castle all the way up to the crowning terraces. The staircase’s design – never before seen in France – seems to suggest a more than coincidental link with the famous Italian polymath, whose notebooks were filled with similar architectural sketches and designs on everything from plumbing to horticulture.
To some, Leonardo’s influence on Chambord is undeniable: its ornamental facades, modular interiors and grid-style layout bear his hallmark elegance and visionary logic; indeed the castle carefully promotes itself as a place “imbued with the spirit of Leonardo”. But it does not claim him as the chateau’s architect, because of a lack of proof. At the quincentenary of the artist’s death – and the castle’s inception – scholars and visitors continue to be ensorcelled by these two enigmas.

It's a long story,here is the link .An ongoing detective story 
http://www.bbc.com/travel/story/20200316-the-unsolved-mystery-of-frances-iconic-loire-valley