a gateway dating from 1873. The 16th-century moat that protected the castle was filled in during the 1860s. The twelve-sided central tower, or keep, is approximately across; it has two storeys and a basement. The inside of the tower is circular, with a spiral staircase running up through a central pillar. The ground floor and first floor rooms would have originally been sub-divided to form living quarters for the garrison, but are now open spaces. Both have eight embrasure windows, suitable for holding lighter weaponry; the first-floor room was sufficiently elevated to have potentially fired out over the external walls. The roof has the remains of gun positions dating from the 1850s and was originally topped by a look-out tower, removed in 1805. When first built, the keep was linked by three bridges to the outer bastions. The two-storied north-west bastion protected the castle against attack along the spit from the mainland, and housed the castle's original portcullis as well as providing accommodation for the garrison. It had three levels of gun positions on its ground floor, first floor, and roof, which were adapted in the 19th century to house heavier weapons and shelter riflemen. The bastion links to an external caponier, a covered walkway with rifle loops for close defence, built in 1852. The north-east and south-east bastions are only one storey tall, originally holding two levels of gun positions on the ground floor and roofs, again both adapted to support heavier guns in the 19th century. West and East Wings The West and East Wing date from the 1860s and are built from brick and stone. They had a lines of gun positions, each designed to hold a heavy gun and a crew of up to 12 men. The positions were protected by granite-fronted casemates and wrought-iron shields, and, with removable window screens, doubled as living accommodation for the crews. Small magazines were positioned behind the lines of casemates. The West Wing is approximately long, and has 37 heavy gun positions and two main magazines, along with various auxiliary buildings, including canteens, stores and detention facilities. It also has two of the castle's lighthouses, an 1865 tower, now disused, and an iron, gas-lit tower, still in use. The garden is a recreation of the garden in the Second World War. The late-19th century and early-20th guns at the castle were predominantly added to the West Wing, and it