Haithabu - Danewerk

The Danewerk in Haithabu, a 15km/9mi long earthwork constructed in the ninth C. and maintained and strengthened until the 13th C., was designed to protect the southern frontier of the Danish kingdom. In the 12th C. the central section was reinforced by the Waldemarsmauer, a brick wall 3.5km/2mi long, 7m/23ft high and 2m/6.5ft thick.