Erected in 1154 as a notable example of the Arab-Norman architecture which flourished in Sicily under Norman rule on the island, the Church of San Cataldo is annexed to that of Santa Maria dell'Ammiraglio. In the 19th century it was restored and brought back to a form more similar to the original medieval edifice.
The church has a rectangular plan with blind arches, partially occupied by windows. The ceiling has three characteristics red, bulge domes (cubole) and Arab-style merlons. The church provides a typical example of the Arab-Norman architecture, which is unique to Sicily. The plan of the church shows the predilection of the Normans for simple and severe forms, derived from their military formation. Moreover, the building shows how international the language of Norman architecture was at the time, as the vocabulary which marks parts of the church, like the bell tower, can be tracked down in coeval buildings like the cathedral of Laon and the Abbaye aux Dames in Caen, both in Northern France, or the cathedral of Durham in England. At the same time, the church shows features shared by Islamic and Byzantine architecture, such as the preference for cubic forms, the blind arches which articulate the external walls of the church and the typical spherical red domes on the roof.
The interior has a nave with two aisles. The naked walls are faced by spolia columns with Byzantine style arcades. The pavement is the original one and has a splendid mosaic decoration. Also original is the main altar.
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.