The Fort de Salses, built 1497-1504, Catalan fortress in Salses-le-Chateau, Languedoc-Roussillon, France. The fortress guarded the former border between Spain and France. It was captured by the French in 1642 during the 30 Years War and became redundant in 1659 with the Treaty of the Pyrenees, when the Spanish border moved South. Its architecture presents the transition between medieval castle and modern fortress. It has very thick walls, mounded earth piled against the internal walls, archer slits, low towers, a deep  moat and a ditch around the keep. Picture by Manuel Cohen