Long a defensive bastion then a prison, the Fort Royal of Sainte-Marguerite Island was bought in 1996 by the municipality of Cannes. Listed as a Historical Monument alongside the island, it now houses Cannes' Sea Museum and an entertainment and accommodation center. The museum allows visitors to discover the interior of the fort's enclosure, the cell of the Man in the Iron Mask, and those occupied by Protestant pastors. It also houses an aquarium room and a space bringing together a large collection of underwater and terrestrial archeology in which ancient Roman cisterns coexist with boats wrecked off the Lérins Islands.