The remains of the Castle can be visited
Regenstein Castle

The Regenstein Castle Ruin, a rock castle in the northern Harz foothills, is near Blankenburg in Saxony-Anhalt. It stands on a sandstone rock and is known for its rooms carved into the rock.
History+
The first documented mention of a Count of Regenstein, Konrad, son of Poppo I of Blankenburg, occurred in 1162. The castle gained fame through Count Albrecht II of Regenstein, who was involved in conflicts with surrounding towns and ecclesiastical dignitaries in the 14th century. These stories later inspired poets such as Gottfried August Bürger and Julius Wolff. In the 15th century, the counts moved their residence to Blankenburg Castle, after which Regenstein Castle fell into disrepair. After the extinction of the comital line in 1599 and several changes of ownership, the site was expanded into a fortress by the Prussians from 1671.
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: 51.8153, 10.9597