Saint-Briac-sur-Mer (Breton: Sant-Briag, Gallo: Saent-Beriac),. III, they established camp in neighboring St Lunaire, but not before pillaging and burning down more than half of Saint Briac. Le Chateau du Nessay (seen below) was built on an emplacement of a castle originating from the 12th century. During the French Revolution, it was used as a prison, to hold political prisoners. St Briac.