The ruins of Nassau Castle rise up near the town of the same name, Nassau, at 215.4 m above sea level. NHN[1] high castle hill, a rock cone 120 meters above the Lahn in the Rhineland-Palatinate Rhein-Lahn district and is a typical example of a hilltop castle. Its builders came from the House of Nassau, which is still the ruler of the Netherlands and Luxembourg. Nassau Castle was first mentioned in 1093 with the mention of Count Dudo von Laurenburg in the first deed of foundation of Laach Abbey. However, since the document is considered a forgery in historian circles, this year is not a reliable indication. The documented beginnings of the castle date back to around the year 1100. In 1120, Ruprecht I of Laurenburg (also Rupert I) and his brother Arnold I took possession of the Nassau castle hill and the residential tower on it. They had the castle complex redesigned and expanded in 1124.
Source: Wikipedia