To be privately owned
Sandsee Castle

A circular fortress, Sandsee Castle, rises near Pleinfeld in Mischelbach, Middle Franconia. The complex, originally conceived as a high castle, is on a vineyard.
History+
The origins of Sandsee Castle probably lie in the 12th century, when it was built by the Lords of Hirschberg. In 1278, a Rüdiger von Dietenhofen is mentioned as administrator. Count Gebhard von Hirschberg sold the castle to the Prince-Bishopric of Eichstätt in 1302, which subsequently used it as an official and hunting residence. During the war between Duke Ludwig of Bavaria and Margrave Achilles of Ansbach, the castle was destroyed in 1462. Bishop Wilhelm von Reichenau had the damage repaired in 1467, as evidenced by a coat of arms on the west wing. Further repairs to the old palas were carried out in 1572 under Bishop Martin von Schaumburg, and a defensive oriel was added in 1621. The Thirty Years' War brought renewed destruction by fire in 1632 and 1636.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Mobile Geschichte
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: 49.1157, 11.0213