The bulwark "Katz," which can only be viewed from the outside, highlights the ongoing conflict between the Counts of Trier and the Counts of Katzenelnbogen, much like its counterpart, the castle "Maus."
The name "Katz" was assigned to the castle in St. Goarshausen by popular usage, which actually originated in 1371 as Castle Neu-Katzenelnbogen. With it, the Counts of Katzenelnbogen aimed to protect their possessions along the Rhine and, in particular, the customs office in the opposite St. Goar - as well as intentionally create a counterbalance to the Trier castle "Maus," which threatened their customs operations. Like many Rhine castles, it ultimately could not withstand the French troops, and the castle was destroyed in 1806. It took almost a century before a historic reconstruction from 1898 to 1899 turned the ruins into a magnificent residence.

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