Alte Burg, 'The old castle', in Burgsinn is a moated castle owned originally by the Barons of Thüngen. In 1337, the Bishop of Würzburg granted the castle and all its possessions as a fief to Dietz von Tungden, who largely built the present castle between 1339 and 1342.
The wide moat surrounding the castle is fed by an underground spring. On the west side, a bridge leads into the castle, which has a trapezoidal layout with towers at its corners. The outer wall is made of rusticated sandstone blocks, while the rest of the masonry is rubble stone, and the southern residential building features timber framing on its upper levels.
The square northeastern tower includes a small elevated residence. A pointed arch door leads into the southeastern tower, which was completed in 1543 by Martin I von Thüngen. The southern wall has been significantly altered with inserted windows, and the round-arched gate at the southwestern tower was fitted with corbels.
The castle complex is dominated by a square, five-story, 22-meter-high keep (dating to the 12th century), constructed of rusticated stones.
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.