Marksburg (castle) built
1117 CE.
Shown on the map at 50.272°, 7.649°.
The Marksburg (German pronunciation: [ˈmaʁksbʊʁk]) is a castle above the town of Braubach in Rhineland-Palatinate, Germany. It is one of the principal sites of the Rhine Gorge UNESCO World Heritage Site. The fortress was used for protection rather than as a residence for royal families. It has a striking example of a bergfried designed as a butter-churn tower. Of the 40 hill castles between Bingen am Rhein and Koblenz the Marksburg was one of only two which was never destroyed (the other being Maus Castle), and the only one that never fell into disrepair.
Text from the Wikipedia article Marksburg, licensed CC BY-SA 4.0.