The Castle can be visited
Roseburg Castle

Roseburg Castle, an imposing edifice, stands majestically on a shell limestone ridge in the Eastern Harz region, near Ballenstedt. Completed as late as 1908, this structure is a remarkable re-creation in the style of a medieval castle, offering a fascinating glimpse into the architectural fantasies of the early 20th century.
History+
The origins of Roseburg date back a long way: a Rudeloffsburg was first documented at this site in 963, a donation by Margrave Gero to the Gernrode convent. In 1056, Emperor Henry III transferred the castle to the Ballenstedt monastery. After changing ownership, which in the 13th century again included the Gernrode convent and later the Ascanian Principality of Anhalt, the Counts of Regenstein pledged the complex to citizens of Quedlinburg. Over the centuries, the original castle fell into disrepair and was no longer mentioned after 1563. It was not until 1905 that architect Bernhard Sehring acquired the site on the recommendation of Prince Friedrich of Anhalt-Dessau.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://commons.wikimedia.org/wiki/File:Ballenstedt_Roseburg.jpg
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: 51.7273, 11.1951