The remains of the Castle can be visited
Königsburg Castle

Southeast of Königshütte, a district of Oberharz am Brocken, the Königsburg Castle Ruin rises, a historic structure in the Harz mountains.
History+
The first documented mention of the Königsburg dates back to 1312, when it was known as “castrum Königshof.” In that year, Bishop Albrecht of Halberstadt acquired the castle from Heinrich von Botvelde. Another mention occurred in 1324 as “castrum Köningshof acqisivit.” After that, the castle fell silent, only to be referred to as “Königsburg” in 1709, by which time it was already a ruin.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Roland Neubert, Halle (Saale)
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 51.7384, 10.7670