The Loire Valley is a living laboratory: Leonardo da Vinci designed his wackiest inventions here, and kings made it the crucible of the French Renaissance. Clinging to the riverbanks, the Chateau de Chambord and its neighbours great and small tell the fabulous story of this artistic effervescence – also expressed by gardens such as those at Chaumont-sur-Loire, which is both a chateau and the landscape laboratory of the future.