Magnificent Dover Castle & Fortress 2000 years defending Britain From the Iron Age to the Nuclear Age, Dover Castle, and before it an Iron Age Fort, has stood defending the narrowest invasion route into the British Isles. The ancient Britons built a huge hill fort on the site, the Roman's built a lighthouse (still standing) here to guide their ships, the Anglo Saxons build a church (still there it became a garrison church), and Norman's built an earthwork and timber-stockaded castle. In the 1180