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:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.