To be privately owned
Ludwigseck Castle (Ersrode)

Ludwigseck Castle, originally a fortress from the early 15th century, stands in Hesse. It is an example of one of the last defensive castles built in Germany, transformed from a stronghold into a stately residence.
History+
The origins of Ludwigseck Castle date back to the early 15th century, when Landgrave Ludwig I of Hesse commissioned the construction of a castle. Its completion in 1419 was supported by the Knights of Röhrenfurth and Holzheim. This fortification served the Landgrave to consolidate his influence over the Hersfeld Abbey. The knightly families initially received the surrounding area as a fief, which from 1432 and entirely from 1449 passed to the Lords Riedesel zu Eisenbach. During the Thirty Years' War, the complex suffered damage but was rebuilt as a castle around 1677.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 50.9856, 9.6244