Ununge Church was probably built at the end of the 13th century, but has been rebuilt and expanded on several occasions. The easternmost part of the church has been dated to the end of the 14th or to the 15th century.
In its layout, the church is a typical example of medieval churches from Uppland. It consists of a rectangular, single-nave church hall consisting of three bays of which the easternmost is the choir. There is a sacristy to the north and a church porch to the south. The oldest of the church fittings are the triumphal cross from the 13th century, which has been described as one of the finest of its kind and Sweden and which resembles contemporary triumphal crosses from Denmark, and the baptismal font, also from the 13th century. The interior of the church was renovated in 1897.
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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.