After the Romans left Günzburg in the fifth century, the Alamanni tribe settled there. In around 700 the nearby castle of Ricinis was mentioned by the Cartographer of Ravenna as one of the five most important castles of Alemannia. In 1065 first documentary evidence appears of the town itself as Gunceburch. In 1301 the town became part of the Habsburg house and was developed into the centre of the Margraviate of Burgau; for a time (1803–1805) it was even the capital of all Further Austria.
After the construction of a castle and church in the south-western corner of the upper town (1577/80), Günzburg became the residence of Archduke Ferdinand II`s son Karl from 1609 until 1618. Margrave Karl was able to bring craft and trade to new heights, but later all his efforts were ruined by the Thirty Year War (1618–1648) in the course of which the number of Günzburg`s citizens went down from about 2,400 to some 800. The castle went up in flames (1703) and the citizens suffered badly under the occupation.
Today the the margraves' castle is the main tourist attraction. It is the only Habsburg castle built in Germany.
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.