The Fortress Ehrenbreitstein on the east bank of the Rhine where it is joined by the Moselle, overlooking the town of Koblenz. Occupying the position of an earlier fortress destroyed by the French in 1801, it was built as the backbone of the regional fortification system, Festung Koblenz, by Prussia between 1817 and 1828 and guarded the middle Rhine region, an area that had been invaded by French troops repeatedly before. The Prussian fortress was never attacked.
Since 2002, Ehrenbreitstein has been part of the #UNESCO World Heritage Site Upper Middle Rhine Valley. Ehrenbreitstein, the hill on which the eponymous fortress is now located, was first settled in the 4th millennium BC, and fortifications were built in the 10th/9th century BC. In the 3rd to 5th centuries AD a Roman fortification was sited there. More settlement followed in the 8th/9th centuries under the Carolingian dynasty. The castle was first mentioned in an extant written document in 1139, as a property of the Archbishop of Trier. Archbishop Hillin expanded it in 1152–1169. A supporting castle (Burg Helferstein) was built on the hill known as Helfenstein to the south.