Viking Age Ring Fortresses
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How it came to be
The Viking-Age Ring Fortresses are five sites in Denmark: Aggersborg, Fyrkat, Nonnebakken, Trelleborg and Borgring. According to UNESCO they were built to a uniform geometric design between about 970 and 980, close to important land and sea routes, and reflect the centralised power of the Jelling dynasty.
Each fortress was enclosed by an exactly circular rampart, with two roads crossing at right angles in the centre and leading to four gates. At Trelleborg on Zealand, tree-ring dating shows the timber was felled in the autumn of 980 and used probably in the spring of 981. Its rampart was 5 m high with a diameter of 137 m, and inside stood 16 longhouses arranged in squares of four.
The largest, Aggersborg, has an inner diameter of 240 m and overlooks a narrow strait of the Limfjord; an Iron Age village was cleared to build it. Both Aggersborg and Trelleborg were used only for a short time. Trelleborg was excavated from 1934 to 1942, while Borgring was spotted as a circle on an aerial photograph in 1970 and dated to the 10th century by research in 2014. The five sites were inscribed on the World Heritage List in 2023.
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