The St. Ursus Cathedral in Solothurn is dedicated to Ursus of Solothurn, who was a 3rd-century Roman Christian venerated as a saint. His his body is located under the cathedral. The first church on the site was built in the Early Middle Ages. St. Ursus of Solothurn was venerated in the city by the 5th century. By 870 there was a college of canons and presumably a collegiate church in Solothurn. A Romanesque church might have existed, but there is no written or archeological evidence to support or refute it.
The first documented record of the Gothic church comes from 1294, while the altars were ordained in 1293 and 1298. It is likely that the twin towers were damaged in the 1356 Basel earthquake damaged, but there is no reliable sources attesting to the damage. It seems likely, since in 1360 the single Wendelstein tower was built above the church and a gothic facade was added to the west face of the church.
The choir was rebuilt in 1544, while the crypt was re-covered. The nave was rebuilt in 1644 and widened. The sacristy was extended in 1664.
By the 18th century the Gothic church was in a poor condition. On 25 March 1762 the Wendelstein tower collapsed forcing the city to begin planning to replace the building. Paolo Antonio Pisoni (1738-1804) took over construction in 1772. On 26 September 1773 the new church was dedicated by the Bishop of Lausanne. The western facade of the cathedral is a monumental white stone neoclassical structure.
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.