An open weekend on 30-31 May 2009 allowed the public to visit the Drop Redoubt, a fortress situated on Dover’s Western Heights.

One of the most important and impressive fortifications in Britain, the Western Heights are a series of strong points linked by miles of ditches on the western hilltop above Dover. They were originally begun during the American War of Independence, were strengthened during the Napoleonic Wars and updated and strengthened again in the mid nineteenth century.
Western Heights Preservation Society

Open days are infrequent, but it is well worth a look around if you get the chance to visit. There are no sound mirrors(!), but the redoubt is very impressive, with immense walls surrounded by deep ditches. The entrance drawbridge is gone, so access is via a tunnel into the moat, and then into the fortress building through a sally port.

There were various re-enactors there and a vintage bus service from the town to the redoubt – though it isn’t far to walk.