To be privately owned
Wartenstein Castle

Wartenstein Castle is a castle complex in Lower Austria. Its origins date back to the 12th century, and it has always been rebuilt and maintained.
History+
The first documented mention of Wartenstein Castle occurred around 1190 by Hermannus de Wartenstein. In the mid-13th century, the complex was first expanded. In 1287, Heinrich von Stubenberg acquired the castle, before it passed to the sovereign in the 14th century and was repeatedly pledged. Around 1470, Emperor Frederick III handed the complex over to the Order of St. George. After a brief occupation by Matthias Corvinus, it reverted to the Habsburgs in 1490. In 1529, Wartenstein Castle was destroyed during the First Siege of Vienna by the Ottomans. Georg Bernhard von Urschenbeck, who had leased the castle since 1547, bought the lordship in 1609. Under Georg Andreas von Petschowitz, renovations took place in the 1640s.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.at/noe/niederoesterreich.html
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: 47.6506, 15.9191