Saints Peter and Paul Mother Church stands on the site of an early church which dated from 1212, retaining its bell tower and two of its stained glass windows. In 1542 it was expanded by the addition of two extra aisles, constructed by Pietro and Antonio Laviola, two brothers who were later accused of murder in Mantua.
The church is in the Romanesque-Renaissance style, with an angled roof, and is built in the shape of a Latin cross, with three aisles. On the left and right there are small chapels, under which there are buried local important people. Each chapel has a statue by the sculptor Salvatore Sacquegna. The interior walls of the church are decorated with 18th-century pictures painted by Domenico Guarino, among which Our Lady of Mount Carmel, the Madonna del Pozzo, and the Mysteries of the Rosary are especially notable.
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.