The Danevirke (modern Danish spelling: Dannevirke; in Old Norse; Danavirki, in German; Danewerk) is a system of Danish fortifications in Schleswig-Holstein. This important linear defensive earthwork across the neck of the Cimbrian peninsula, was initiated by the Danes in the Nordic Iron Age at some point before 500 AD. It was later expanded multiple times during Denmark's Viking Age. The Danevirke was last used for military purposes in 1864 during the Second War of Schleswig.