From the Flanders Dunes, owned by the Conservatoire du Littoral and where crested larks and Haflinger horses live side-by-side, to the watergangs fringed by reedbeds, Flanders Opal Coast, so long threatened by the waters of the sea, is now a precious land and the object of much care and attention. And the chief guardians of this natural heritage are Bergues and Gravelines, towns fortified by Vauban.