The Royal Citadel, Plymouth was original built in 1660s as a bastion fortification. At its’ height the Citadel mounted some one and thirteen smooth bore guns. The Royal Commission on the Defence of the United Kingdom recognised the continuing importance of the Citadel as a barracks and concentration point. The Royal Garrison Artillery (RGA) had their barracks here and the location was used for training.
From 1860 onwards the Inner and Outer defences of Plymouth Harbour were built away from the Citadel.
A Submarine Mining Establishment was built on the South side of the Citadel between 1884 and 31st March 1888.