Bertradaburg

This imposing castle complex, located on a mountain spur above the village of Mürlenbach, goes back to a protective foundation of the Prüm Abbey. A thicket of medieval sagas and legends lets the castle appear in a mysterious light.
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The castle owes its name to Charlemagne's great-grandmother, Bertrada the Elder, who is said to have lived here with her son. Allegedly, Charlemagne is said to have even been born on Bertradaburg.
There is the possibility to learn more interesting facts about the castle as part of one of the regular guided tours. Guided tours take place every first Sunday of the month from May to October at 3 p.m. and for groups by appointment. Registration and further information under Tel. 06591 984949. Source: eifel.de/go/sehenswertes-detail/322.html

The Bertradaburg is the ruin of a hilltop castle at 348 m above sea level. NN high rock spur above the local community Mürlenbach in the Vulkaneifel district in Rhineland-Palatinate. It is thus in the geographical center of the Merovingian Franconian Empire.
The castle was built on the remains of a Roman fort, which presumably served to protect the Roman road from Trier to Cologne. According to local tradition, Bertrada, the mother of Charlemagne, lived in the castle, which suggests that he was born around 747. The existence of the castle is first documented in the 13th century as a state fortress of the prince abbey of Prüm, but archaeological evidence suggests that the castle complex was built earlier
Source: Wikipedia