Stahleck Castle is a hilltop castle in the Middle Rhine Valley in the area of the town of Bacharach in the Rhineland-Palatinate district of Mainz-Bingen, almost 50 kilometers south of Koblenz. Its water-filled ditch is a rarity in Germany.
The name of the castle is made up of the Middle High German words stahel for steel and ecke as a designation for a mountain spur and means invincible castle on a mountain spur. It was probably built at the end of the 11th or beginning of the 12th century and was a fiefdom of the Electorate of Cologne. Since Bacharach had become a trading and stacking place for the Palatinate-Rhinegau wine trade under the Counts Palatine near the Rhine, the complex also functioned as a customs castle.
From the beginning of the 13th century, Stahleck was owned by the Wittelsbach family and remained there until the beginning of the 19th century, although it was besieged and conquered a total of eight times by various parties during the Thirty Years' War. Badly damaged by explosions in the Palatinate War of Succession in 1689, after the end of the Palatinate Electorate, Stahleck was in ruins and property of the French state, which had to cede it to the Kingdom of Prussia in accordance with the provisions of the Congress of Vienna in 1815.
The Rhenish Association for the Preservation of Monuments and Homeland Security, which was based in Koblenz at the time, acquired the castle complex from the Prussian domain administration in 1909 and had it rebuilt as a youth hostel from 1925. The expansion during the 1920s and 1930s served as a role model throughout Germany. However, the castle was not fully restored until 1967, when work on the keep was completed. The youth hostel has continued to this day, so it is not possible to visit the interior. However, the large viewing terrace offers a good view of the Upper Middle Rhine Valley there, as part of which the complex has been a UNESCO World Heritage Site since 2002. Because of its importance as a particularly valuable historic building, Stahleck Castle has also been under protection since 1989 under the terms of the Hague Convention.