Fort Diamant is a ruined coastal fort near Rémire-Montjoly, southeast of Cayenne. Its walls and position recall the period when French Guiana's coast needed watching as much as settling, with batteries placed to cover approaches around the Mahury area.
Do not expect a heavily interpreted monument. The reward is the mix of sea air, colonial military remains, and a quieter edge of the Cayenne area, best visited as part of a loop through Rémire's beaches and coastal viewpoints.