In the south-east corner of the ramparts is the One-Gun Battery, which originally held a "disappearing gun", designed to pivot back under a steel shield when fired. Built in 1895, the approach proved unsuccessful and the gun was removed in 1913, but the emplacement still remains and is a rare survival of this type of weapon.; The Bell Bastion, the Ravelin, the Pig's Pound Bastion and the Horse Pool Bastion protect the southern and western parts of the ramparts. A range of artillery and anti-aircraft guns are on show around the defences, including 19th-century carronades, and 20th-century pieces such as a 155 mm (6.1 in) Long Tom field gun, a Quick Firing 3-inch 20 cwt (76 mm 102 kg) anti-aircraft gun and two Ordnance Quick-Firing 25-pounder (11 kg) howitzers.
