Adendorf castle is the successor of a high-medieval castle located to the west of today's site. The small castle hill is few hundred meters from the current palace and was in the 14th century owned by the family of Hüchelhoven.
Arnold von Adendorp built a new castle from 1337 at its present location. It was besieged and conquered by the army of Henry III, Landgrave of Upper Hesse, in the late 15th century.
In 1659-1663 the medieval castle was transformed as a representative Renaissance schloss. Another reconstruction took place in 1842. The changes included the filling of the moat between the outer bailey and main building.
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.