 The main defensive structure is a <unk> lunette shaped <unk> . It has a 15 @-@ metre ( 49 ft ) thick rampart with 1 @.@ 5 m ( 5 ft ) of concrete and 0 @.@ 6 m ( 2 ft ) of brick forming a retaining wall for the earth fill . The rampart is covered by natural vegetation and , in both the 19th and 21st century operation , is closed to access to preserve this . The glacis gives extra protection to the fort and was designed to blend the fort into the landscape . It surrounded the fort on the north , south and seaward sides and was made by forming the surrounding <unk> . The side facing the fort — the <unk> — is steep and , with the front face of the rampart , forms a 12 ft ( 3 @.@ 7 m ) wide ditch that can be raked by rifle fire from the caponier or the stockade 's sides . The outer face is a gentle slope and is designed to be covered by case shot fired from the fort 's 64 @-@ pounder guns . The southern glacis section was removed during sand mining and construction of the caravan park , both after World War II . The western glacis is changed , but still visible , and the northern glacis was recreated in 1993 — showcasing the purpose of the glacis and the function of the caponier . <unk> to the fort is via double gates at the fort 's rear , one each through the stockade and the rear defence wall . Both gates were removed or destroyed over time and the 21st century gates are reconstructions . The formal parade ground or manning parade lies between the rear walls and barracks , and the raised terreplein . It was formerly used for drill training , assembly and formal parades . First <unk> when constructed , it was paved with tar in the 1890s to solve drainage problems . Around the seaward side of the manning parade runs the terreplein . It is a raised crescent shaped level on which the guns platforms sit , and is ascended from the manning parade by ramps and stairs . 
