This explains everything

From Wikipedia: "The castle is built on rock approximately 40 metres (130 ft) above the level of the river Danube. A Roman fortress may have stood there before. The castle was begun in the early 12th century by Marchwardus de Schoenbuchele as a defensive fortress. When his descendant Ulrich von Schonpihel died at the beginning of the 14th century, the family was extinguished. The castle was briefly owned by Conrad von Eisenbeutel, and then by the Abbey of Melk. In 1396 it was sold to the brothers Caspar and Gundaker von Starhemberg. It remained in the Starhemberg family for more than 400 years, but fell into disrepair. In 1819 Prince Ludwig Josef von Starhemberg sold it, together with the castle of Aggstein, to Count Franz von Beroldingen, who had it renovated and partially rebuilt, so that by 1821 it was again habitable. In 1930 the Schönbühel estate was sold to Count Oswald von Seilern und Aspang."