the ancient frontier rampart of the Danes against the Germans, extending 10.5 miles (17 kilometres) from just south of the town of Schleswig to the marshes of the river Trene near the village of Hollingstedt. The rampart was begun about AD 808 by Godfred (Gudfred), king of Vestfold. In 934 it was penetrated by the German king Henry I, after which it was extended by King Harald I Bluetooth (c. 940–c. 985); but it was again stormed by the German emperor Otto II in 974. After the union of Schleswig and Holstein under the Danish crown in the 15th century, the Danewirk fell into decay; but in 1848 it was hastily strengthened by the Danes, who were, however, unable to hold it in face of the superiority of Prussian artillery, and on April 23 it was stormed.

From 1850 onward, Danewirk was again repaired and strengthened at great cost and was considered impregnable; but in the war of 1864 the Prussians turned it by crossing the Schlei, and it was abandoned by the Danes on February 6 without a blow. It was thereupon destroyed by the Prussians. In spite of this destruction, however, a long line of imposing ruins still remains. The systematic excavation of these, begun in 1900, yielded some notable finds, especially of valuable runic inscriptions.