The Kyffhäuser (German pronunciation: [ˈkɪfˌhɔɪ̯zɐ],[1] sometimes also referred to as Kyffhäusergebirge) is a hill range in Central Germany, shared by Thuringia and Saxony-Anhalt, southeast of the Harz mountains.

The settlement of Tilleda, located below the northern rim of the range, was already mentioned as Dullide in the early 9th century in the Breviarium Sancti Lulli register of Hersfeld Abbey.

During the 11th century, Tilleda was superseded by a castle on the hill above the settlement that may have been erected by Emperor Henry IV during the Saxon Rebellion.

In 1698 Count Albert Anton of Schwarzburg-Rudolstadt had a Baroque hunting lodge erected at the hamlet of Rathsfeld in the centre of the Kyffhäuser range.

According to a king asleep in mountain legend, Emperor Frederick Barbarossa, who actually drowned on 10 June 1190 in the Calycadnus River near Seleukeia in Asia Minor during the Third Crusade, is not in fact dead, but sleeps in a hidden chamber underneath the Kyffhäuser hills.

As in the similar legend of King Arthur, Barbarossa supposedly awaits Germany's hour of greatest need, when he will emerge once again from under the hill.

The Barbarossa myth was first documented in the late 17th century and later popularized by the Brothers Grimm and a poem written in 1817 by Friedrich Rückert.