A circular fort 180 feet across, built in 1808 when a Napoleonic invasion still seemed plausible. The design is compact and self-contained: ten guns on the battlements, eighteen casemates that could house 300 troops in a siege, and a dry moat around the perimeter. It was never attacked, but it remained in military use until after the Second World War. Today it is maintained by volunteers and is open for tours in summer.
Harwich Redoubt
Circular Napoleonic fort with summer volunteer-led tours