An extremely impressive 180ft (60m) diameter circular fort built in 1808 to defend the port of Harwich against a Napoleonic invasion. Ten guns sit on the battlements. Eighteen casements below would house 300 troops in siege conditions. Part of the fort is now used as a military museum. Battle re- enactments and other events are held during the summer months. The fort was restored by the Harwich Society as a voluntary project.