The Harzburg, also called Großer Harzburg, is a former imperial castle on the edge of the Harz mountains directly above the spa resort of Bad Harzburg in Goslar district in the German state of Lower Saxony.
The castle has almost completely disappeared; only fragments of the foundation walls and the towers together with the well have survived.
The Große Harzburg (Hartesburg) was erected during the castle building programme in Saxony from 1065 to 1068 and was strategically sited by King Henry IV. Henry’s architect was later the Bishop of Osnabrück, Benno II. The castle provided protection for the nearby Imperial Palace of Goslar. Its walls extend right up to the steep face of the conical mountain top. At the time it was built the castle was impregnable. Despite its defensive strength, the castle was also especially palatial. For example, it contained, amongst other things, unusually large, three-roomed great hall and collegiate church, to which Henry had many relics transferred. He even had a sort of family vault built, in which he laid the bones of his brother, Conrad and his son, Henry, both of whom died young.
At the start of the Saxon Rebellion in 1073, Henry IV had to flee along with the imperial insignia from the Imperial Palace of Goslar into the Harzburg. The besieging force allegedly numbered 60,000 whilst his garrison only had 300 men. The king finally fled, according to legend, through the well of the besieged castle and a secret passage. In the Treaty of Gerstungen of 2 February 1074, Henry was forced to agreed to slight his castles, including the Harzburg. He hesitated, however, and only had the walls and towers demolished, whilst the buildings themselves remained. But in the spring of 1074 the Harzburg was plundered by angry farmers in the area and completely destroyed. The collegiate church was not spared and the royal family tomb was desecrated. This gave Henry cause to advance with all his might against the rebellious Saxons again and so, on 9 June 1075, the Saxons rebels were defeated at the First Battle of Langensalza.
Under Emperor Frederick I, the rebuilding work on the castle continued until 1180 and was completed by Emperor Otto IV, who died in 1218 at the castle itself. The Harzburg lost its immediate function as an imperial castle because Emperor Otto IV had to surrender the imperial regalia to the Hohenstaufens. However, in 1222 the Harzburg was awarded the title of castrum imperiale again, and the character of the castle as an imperial fortress remained largely intact up to the time it was pledged (1269) using the existing imperial enfeoffment of the Harzburg seat.
This was followed by frequent changes of ownership. In the 15th century it was pledged as a fief to three brothers from Schwicheldt who turned it into a robber baron castle. The importance of the fort decreased steadily, resulting in its slow decline. A rebuilding of the castle in the 16th century was never carried out due to the high cost. During the Thirty Years’ War, the castle changed hands several times, although its complement remained intact. Since this type of fortification had become insignificant due to the changed nature of warfare, demolition of the remaining elements of the ruin began in 1650. Since then the castle has amounted to little more than its foundation ruins and well. The urban settlement of Neustadt at the foot of the Großer Burgberg adopted the castle’s name.