St. Olof's Church was originally built around the year 1100 and it consisted of a main tower, chancel and nave. It was later extended, but the construction was probably interrupted when archbishop’s seat was moved to Gamla Uppsala in the 12th century.
St. Olof's church has been influenced by the Nidaros Cathedral in Norway, while the small tapering windows have an Anglo-Saxon style. The church is dedicated to the Norwegian viking Olaf Tryggvasson, king between 995-1000.
It is not certain by whom the church was built. Most probably it was authored by the Benedictines or local trade guild. Archaelogical excavations have revealed remains under the church, which are thought to have belonged to an even older stone church. It may have been one of the first built in Sweden.
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.