India, April 1 -- Built in 1519, the iconic castle in Loire Valley of France, from the Renaissance period, doesn't have an official architect till date. By Tanvi Jain

Chteau de Chambord, the largest castle in Loire Valley of France, located 50 kilometres east of Amboise - a town on the southern bank of the Loire River in France - is still in search of its architect, even after 500 years of construction. Built in 1519, the castle commissioned by King Francis 1, is considered one of the most impressive works of French Renaissance and Medieval Revival architecture.

The most iconic feature of Chambord remains its double helix staircase. This unusual staircase, comprising two helical ramps, that twist like a DNA strand around a hollow core,...