Château de Chambord. The designed changed considerably between the starting of construction on 6 Sep 1519 till 28 yrs when it was finally complete in 1547.  It consists of 440 rooms, 282 fireplaces, and 84 staircases, including its spectacular double helix staircase as the centre piece.  It was the inspiration for 1991 Walt Disney's Beauty and the Beast castle.  It now is one of the most recognisable châteaux in the world due to its very identifiable French Renaissance architecture that has a mix of classical French medieval style with traditional Renaissance buildings.