Zwingenberg Castle dates from the 13th century. In the 1326 the lords of Zwingenberg were mentioned as an owner. In 1364 the castle was conquered and destroyed by the imperial forces. The fortress and estate were then immediately divided in two equal parts and bought by the Palatinate and the archbishoprie of Mainz. The reconstruction of the castle was made by the brothers Hans and Eberhard of Hirschhorn in 1404. The brothers were invested with the castle by Mainz and the Palatinate. We owe the building as it appears today essentially to them.
In 1778 Karl Theodor of the Palatinate conferred it upon his natural son the count of Bretzenheim; the count’s mother the countess of Heydeck, was buried in the castle chapel, where her tomb still stands today.
in 1808 the palatinate was divided up upon Napoleons orders the new sovereign the Grand Duke Karl Friedrich of Baden purchased it with his own private means. Since then it has been family property of the house of Baden.
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.