To be privately owned
Gersdorfer Castle

Gersdorfer Burg, a historic complex near Quedlinburg, combines the remains of a medieval fortification with more recent farm buildings. Originally built in the 12th century, it shows the development of rural settlements and the adaptation of historical structures to new uses.
History+
The origins of Gersdorfer Burg date back to the first half of the 12th century. The associated settlement, bequeathed to the Quedlinburg Abbey in 961, was already abandoned by the 1260s. The castle itself was temporarily owned by the Counts of Regenstein and was destroyed in 1337. A first reconstruction took place in 1369.
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: 51.7635, 11.2092