To be privately owned
Calenberg Castle

Calenberg Castle, a historic hilltop castle, was built around 1250. It is on the eponymous Calenberg in the Calenberg district of Warburg.
History+
The origins of Calenberg Castle date back to approximately 1250, when it was built by the Lords of Berkule. It was first documented in 1299. In 1307, Bishop Otto of Paderborn enfeoffed the Westphalian family of Papenheim with the castle, who subsequently adopted the name Rave von Calenberg. This enfeoffment was renewed in a 1326 treaty, which already referred to the location as a town. After the death of the last Rave von Calenberg in 1464, a feud over the inheritance erupted between Landgrave Ludwig II of Hesse and the Bishop of Paderborn, which was only settled in 1471. In 1868, the merchant Hugo Schuchard acquired the Calenberg estate, including the castle. He had the outbuildings demolished and a new manor house built.
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: 51.4655, 9.1646