Deal Castle retains most of its original 16th-century structure, including a tall keep with six semi-circular bastions, 86 feet (26 m) across, at the centre, flanked by a further six rounded bastions, the western of which served as a gatehouse, surrounded by a moat and a curtain wall.[69] The castle's bastion walls are 15 feet (4.6 m) thick.[70] It was constructed using Kentish ragstone from near Maidstone, locally made bricks and Caen stone recycled from local monasteries.[71] It was larger than its sister castles at Walmer and Sandown, measuring approximately 234 by 216 feet (71 by 66 m) across and covering 0.85 acres (0.34 ha).[72]