The oldest parts of Guldrupe church is the nave, dating from the late 12th century. Oak planks decorated with dragons have however been found on the site, and indicate that there may have existed an earlier, wooden church on the spot. The tower dates from the early 13th century, and from the end of the same century dates the un-proportionally large choir and sacristy. The choir replaced an earlier, smaller choir, but plans to replace also the nave were never carried out. The church has not been substantially altered since the Middle Ages. The windows date from 1865 and the church was renovated in 1964-65.
The church is built of limestone. The nave and tower are Romanesque in style, while the somewhat later and larger choir is Gothic. The pyramidal tower spire is unusual in that its construction is largely original.
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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.