From Wikipedia....

The château of Sully-sur-Loire dates from the end of the 14th century and is a prime example of medieval fortress. It was built at a strategic crossing of the Loire river.

The château was expanded by Maximilien de Béthune, first duke of Sully and Minister of King Henry IV of France (1560–1641), who is buried on the grounds of his château. The family of the dukes of Sully retained ownership of the château until the 20th century.