Brömserburg

The Brömserburg is located near the banks of the Rhine in the town of Rüdesheim am Rhein in Rheingau-Taunus-Kreis in the German state of Hesse. Its original structure was probably one of the first stone castles in the Rhine Gorge, now a UNESCO World Heritage Site.
The older literature suggested the Brömserburg was built on the foundations of a Roman fort. However, no antique building fabric has been confirmed and, in particular, it remains unproven that, as previously assumed, it was a watchtower or the bridgehead of a crossing opposite Bingium on the left bank of the Rhine. Since this fort was only built in the 4th century, the thesis is not conclusive, because the Romans had already withdrawn from the right bank of the Rhine after the fall of the Limes.

Wikipedia