Sankt Pölten Cathedral has been the episcopal seat of the Diocese of Sankt Pölten since 1785, having previously been the church of the Augustinian Abbey of St. Pölten, dissolved in 1784. The building, despite being a well-preserved late Romanesque structure, is Baroque in appearance.
The use of the site for religious buildings is believed to date from around 790, when a Benedictine monastery was established here, to which were brought the relics of Saint Hippolytus, after whom the present city is named. In 828, the monastery became a possession of the Diocese of Passau, and a centre of missionary activity, predominantly in Great Moravia. After the invasion of the Magyars in around 907, the monastery was almost entirely destroyed, and was not rebuilt until after the Battle of Lechfeld in 955. The first documentary reference is in a charter of 976 from Emperor Otto II to Bishop Pilgrim of Passau.
Under Bishop Altmann of Passau the abbey became an Augustinian canonry, which was dissolved in 1784 as part of the Josephine Reforms.
In around 1150, the abbey church was rebuilt with three naves but no transept, with a westwork including two towers. In 1228 Bishop Gebhard changed the dedication, formerly to Saints Peter, Stephen and Hippolytus, to the Assumption of Mary. After a fire it was rebuilt again between 1267 and 1280. After another fire in 1621 the entire building was remodelled in the present Baroque style.
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.