To be privately owned
Wenigenburg Castle

The Wenigenburg in Gudensberg, Hesse, is a former Romanesque hilltop castle that once served as an outwork to the Obernburg. It is now privately owned.
History+
The exact construction date and builder of the Wenigenburg are unknown, but it is believed to have originated from an economic farm of the Obernburg and was already fortified during the time of the Hessian Gau counts. In 1272, guards of the castle, also known as Unternburg, were paid by Landgrave Heinrich I of Hesse. Count Heinrich IV of Waldeck recaptured the castle for the Landgraviate of Hesse in 1312. Its final destruction occurred on September 2, 1387, during the siege of Gudensberg by the Archbishop Adolf I of Nassau of Mainz, after which it was not rebuilt. Parts of the ruin were later used for Gudensberg's city fortifications. The current buildings likely originated in the 16th and 17th centuries.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://de.wikipedia.org/wiki/Wenigenburg_%28Gudensberg%29#mediaviewer/Datei:Gudensberg_Wenigenburg.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: 51.1769, 9.3651