The remains of the Castle can be visited
Alte Burg Osterode

The Alte Burg Osterode is the ruin of a spur castle in Osterode am Harz, Lower Saxony. A remnant of the keep remains today, situated on a cemetery ground and open for visitors.
History+
The first documented mention of the Alte Burg dates back to 1153. In the 12th century, it belonged to Henry the Lion and, after his death, passed to his son Otto IV. Later, Otto the Child inherited the castle, followed by Albrecht the Long and Henry the Wondrous as further owners. In the 14th and 15th centuries, the castle served as a residence for the Dukes of Grubenhagen and as a dower house. The last resident was Duchess Elisabeth, who died in 1513. After her death, the decay of the complex began.
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: 51.7299, 10.2571