The remains of the Castle can be visited
Grasburg Castle

The Grasburg castle ruin, a former refuge castle, is situated in the South Harz near Rottleberode. This early historical site is characterized by its preserved rampart and ditch system and is, according to legend, the original home of the Counts of Stolberg.
History+
The origins of Grasburg date back to early history, where it served as a hillfort with a defensive system. Although it is considered the ancestral castle of the Counts of Stolberg, historical theories about their exact lineage have not yet found definitive confirmation.
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: 51.5183, 10.9349