A behavior like "cat and mouse" is not just a saying: The quarrels of medieval lords were equally reflected in their construction activities.
Thus, the castle known as Deuernburg, or "Mouse," is ultimately a counter-castle to the castle "Cat" in the conflict between the Counts of Katzenelnbogen and Electoral Trier. Castle "Mouse" was established in 1356 by the Archbishop of Trier, Boemund II, in St. Goarshausen-Wellmich - and was directed from the beginning against the upstream Rheinfels, a castle of the aforementioned Counts of Katzenelnbogen. They did not take long to react to the threat to their customs clearance in St. Goar posed by the new Deuernburg on the opposite bank of the Rhine, and completed their castle Neu-Katzenelnbogen - later called Castle "Cat" - as a hostile response even before 1371. The two fortresses together rank among the most well-known attractions in the Rhine Valley. Unlike the "Enemy Castle Cat," the "Mouse," with its core structure rebuilt since 1900, gives an impression of medieval castle construction.

The castle is privately owned and currently can only be viewed from the outside.