Schönbühel castle origins date from the early 12th century. The castle is built on rock approximately 40 metres 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 Ludwig Josef Gregor von Starhemberk 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.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.