Caerphilly Castle is an impressive 13th century stone concentric fortress, founded by Gilbert de Clare. The large central island, is protected by lakes to the north and south, a fortified screen wall to the east, that forms a barbican and a ward with a stone revetment to the west. The high curtain wall of the inner ward, is defended on the angles by huge circular towers and dominated by a massive keep-gatehouse. The lower outer curtain wall is flanked by open bastions and two twin-turreted gateways. The castle is one of the largest medieval fortresses in Britain and a supreme example of military fortifications, supported by extensive and unique water defenses. A mound to the north-west is a Civil War artillery redoubt, built on the site of a Roman fort. One and a half miles east is Gwern-y-Domen and 7 miles south is Cardiff Castle.