Keep The fortified stronghold at the centre of the castle. Originally all the living quarters and stores were also in the keep.
Curtain wall The external wall of the castle. The seaward side of Southsea Castle remains in its original position, but the northern side was completely rebuilt in 1814 to extend the castle and provide living quarters for a larger garrison of 200 men.
Tudor wall The line of the original Tudor wall can be seen in the courtyard in the area adjacent to the well.
Counterscarp gallery A gallery running around the moat, this feature was added in 1814.
Caponier The caponier is a bomb-proof passage under the moat leading from the inside of the castle into the counterscarp gallery.
Glacis Earthwork on the outside of the moat slopes gradually from the top of the moat to ground level. This us the glacis and was designed to reduce the target area of the castle for enemy gunners. It was added in the late 17th century. The shape of the glacis has been lost in later 19th century work to add flanking batteries on either side of the castle.
Lighthouse Southsea Castle’s lighthouse was added in the 1820’s to aid navigation for vessels using the deep water channels. It was still in use until very recently, playing a central role in the navigational system for ships entering Portsmouth Harbour. With the arrival of the HMS Queen Elizabeth II carrier, new lights were added out to sea.