The church on the site of current San Dalmazzo is documented from the 11th century, but the present church was reconstructed in 1702. In 1885 the interior was redecorated in neo-gothic style. Adjacent to the church is the former convent and school of the Barnabite order. From 1271 to 1606, the church had been linked to the Order of Canons Regular of Sant'Antonio of Vienne, but then was transferred along with the convent to the Barnabites.
The nave was painted by Enrico Reffo in 1895–1916. The interior also contains 18th century canvases and an antique baptismal font.
Between 1629 and 1631 the chapel of the Madonna of Loreto was built, imitating the Casa Santa (Holy House), which contains an icon related to Marian Apparitions.
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.