The Drop Redoubt is one of two forts,which make up part of the Western Heights at Dover. The Redoubt is linked via dry ditches to the other fort "The citadel". They were built to defend the Port of Dover from attack in the 19th Century.
The Drop Redoubt was first started in 1804 and was in the shape of a pentagon. Inside were Barracks for 200 troops,a magazine and Artillary.
The remains of a second century Roman lighthouse (Pharos) were discovered in the Redoubt,called the "Bredenstone",it is sometimes known locally as the Devils "Drop" of Mortar. Another better preserved Pharos is at Dover Castle.
After the Royal Commision of 1959 the Redoubt had four Caponiers and gun ports built to defend the dry ditches around the fort. The Magazine was enlarged,and the Officers Quarters,Guardroom and Cells were added at this time to. Also the rest of the Western Heights was built in this period.
In WWII the Redoubt was home to a secret squad of Commando's,that in the event of an attack by the Germans,the Commando's would of destroyed the harbour. A small tunnel has been cut through from the dry ditch to the outside for access.
Today the Drop Redoubt and Western Heights are looked after by the voluntary run Western Heights Preservation Society (WHPS) and they have a couple of open days each year.
Please see there website for more details on the Western Heights and open days:
http://www.dover-western-heights.org/index.html