The fortress of Matignon was built in 1559 as a quadrangular fort with a round tower, cellars, a bakery, and a cattle shed. This was expanded in 1740. The English destroyed the fort in 1744. A new fort was built at the other end of the island, which the English destroyed in 1756. In 1772, the Louis XV granted the archipelago to the Abbot Nolin. Napoleon III ordered the construction of the present fort in 1859, and the work was completed by 1866. The fort then served briefly as a prison for Communards in 1871. Although the fort ceased to be a military site in 1906, during World War I it held some 300 German and Austrian prisoners of war. The automobile engineer Louis Renault purchased it and restored it between 1922 and 1924, with the result that it became known as Château Renault. He used it as a retreat from business. During World War II German soldiers garrisoned the fort. Today it serves as the home for several fishermen.