The northeastern corner of the old city fortifications was built starting in 1324. The 26m high octagonal tower made of broken stone masonry stands in the middle of a 97m long preserved section of the old city wall.
On the ground floor is the former prison of the city of Lahnstein.

A spiral staircase leads up to the second floor with the Schöffensaal. Formerly the watchroom of the tower garrison, it is now used for receptions of the city administration and weddings. The tower also houses the museum of the city of Lahnstein, which documents the rich history with coats of arms, seals, and documents.