Henneburg Castle lies on a hill on the right bank of the Main River in the town of Stadtprozelten. Schenken von Klingenberg family built it as a border fortification around 1200. It was the residence of the Teutonic Order for almost 200 years and last served as the official residence of the noble Mainz Amtskeller officials.
It was deserted in the 16th century andfell into disrepair over time. The castle grounds are broken down into the upper castle, consisting of a fortification and main castle, as well as the outdoor grounds with moat and rampart and the defensive wall on the Main river side. The fortifications surrounding the upper castle, several castle gates, seven wall towers or their remains, both Great Hall ruins, the large and small keep and the roughly 150 metre long underground wall-walk accessible through exits in the wall towers, which links the south-west gateway to the northern part of the castle remain intact.
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.