Dannevirke is an ancient system of fortifications that run for 30 km across the neck of the Jutland peninsula.
According to written sources, Dannevirke was built in 808 by King Gudfred as a defense against the Carolingian Empire of Charlemagne (742-814). The Dannevirke was then strengthened by Queen Thyra Dannebod in the second half of the 10th century. Modern archaeology has shown that the Dannevirke is actually much older than that.
The latest excavations in 2013 show that the Dannevirke dates from at least 500 AD and may even be older than that.
The Dannevirke consists of a bank and ditch system between 3.5-6 metres high. In the Middle Ages, it was reinforced with palisades and masonry, and Danish armies would gather here before moving south into Germany. The Dannevirke has been strengthened over the years and was considered impregnable at the time of the Second Schleswig War of 1864. Unfortunately, the Prussian and Austrian armies were able to overrun Dannevirke in the war quite easily because of weather conditions. Frosty weather made it possible for the armies to simply go around the fortification and the practical use of the fortification came to an end. However the myth of the Dannevirke as the fortification protecting Denmark was still powerful and it functioned as a potent symbol for 19th century Danish nationalism.