To be privately owned
Lahneck Castle

Lahneck Castle, a spur castle, stands on a steep rock spur above the left bank of the Lahn River, near its confluence with the Rhine in Lahnstein-Oberlahnstein. Its symmetrical, elongated rectangular layout is characteristic of late Staufer castles.
History+
Archbishop Siegfried III of Eppstein, Elector of Mainz, began construction of Lahneck Castle in 1226 to protect his territory at the Lahn estuary. The region, including Lahnstein and the Tiefenthal silver mine, had come under the control of Electoral Mainz in 1220 through an imperial fief. In 1245, the castle chapel was built, and a burgrave named Embricho von Lahneck was first mentioned. King Adolf of Nassau was a guest at the castle in 1298, shortly before his death in the Battle of Göllheim. The Lahneck burgrave Friedrich Schilling von Lahnstein avenged the king and was executed in 1309 after the castle was stormed. In 1332, Pope John XXII granted an indulgence for visiting the castle chapel, dedicated to Saint Ulrich. In 1338, Elector Heinrich III von Virneburg participated in the Electoral Union of Rhense from Lahneck Castle. In 1400, the four Rhenish Electors meeting at Lahneck Castle declared King Wenzel deposed.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Rainer Gindele
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: 50.3063, 7.6125