Burg Rheinfels (Rheinfels Castle)

From www.igougo.com:

Burg Rheinfels, the mightiest fortress ever constructed on the banks of the Rhine towers over St Goar. The original castle was built by Graf Dieter V von Katzenelnbogen in 1245. On completion he did the obvious thing and increased toll charges on boats plying the river below. In response 26 Rhine towns banded together and raised an army of 8000 men and 1000 knights. The fortress was encircled for a year and 14 weeks before the union retreated in defeat. After the much feared and famously powerful Katzenelnbogen family died out in 1479 the castle came into the hands of the Hessen family. The Hessens continued expansion work including underground tunnels from where advancing enemies could be surprised.

The French failed to conquer the castle in 1692 when a force of 18,000 with 10,000 backups faced a garrison of 3,000. Despite ten days of artillery bombardments the French had to retreat with 4,000 dead and 6,500 wounded - eight times more than the Germans. A century later in 1794 the coward commander fled before the advancing French army and the castle fell without a shot being fired. However, it was later systematically blown up. Reconstruction started during the nineteenth century.