St. Michael's Church was built in the Early-Gothic architectural style, first mentioned in 1282, in 1449 burned down by a fire and subsequently rebuilt. The expansion work on the church in the fifteenth and sixteenth-century was blighted by the Thirty Years' War and as such was burned down again. Prior to 1671, the church was renovated by Bishop of Wrocław, Sebastian von Rostock. The church was restored in 1893.
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.