The Marksburg is a castle above the town of Braubach in Rhineland-Palatinate, Germany. It is the only medieval castle of the Middle Rhine that has never been destroyed. It is one of the principal sites of the UNESCO World Heritage Rhine Gorge.
The castle was built to protect the town of Braubach and to reinforce the customs facilities. It was built about 1117 and explicitly first mentioned in 1231. www.marksburg.de/