The Palatinate near Kaub, sometimes incorrectly called the Rhine Palatinate or Pfalzburg, is actually called Pfalzgrafenstein. The island castle on the Weisenau cliff could serve much better as a toll tower in the middle of the river, since Gutenfels Castle was far too far from the shore. Ludwig the Bavarian (1314-1347), the Count Palatine near the Rhine and later German-Roman Emperor, had a toll tower built in a surprising action between August 1326 and July 1327.
At the same time, the customs office in Kaub, where the duty was collected, was to be secured. In contrast to most other castles and palaces on the Rhine, the Pfalzgrafenstein was built exclusively for economic reasons: it always served as a base for customs collection. Lying on an island in the middle of the Rhine, this function is also evident from the location. Anger even reached the Pope when the wine boatmen of the monasteries and prelates had to pay duty to the Count Palatine. Today it is hard to imagine that the ships between Mainz and Cologne had to stop at twelve customs posts.
The medieval customs castle rises up from the middle of the Rhine like a stone ship and provided a good source of income for various feudal lords for several centuries.
However, Pfalzgrafenstein was not the actual customs station, as ships could not dock there. The task of his crew was to spot the ships and to ask them to stop with a trumpeter