 It was later used as a depot for convicts on their way to the penal settlements of New Caledonia and French Guiana.Prisoners included Alfred Dreyfus, en route to the penal colony of Devil's Island after his conviction for treason.The old city of Saint-Martin, within the walls of the citadel, was added in 2008 to the World Heritage Site list, along with 11 others Fortifications of Vauban across France.