Nardò Cathedral has been since 1986 the episcopal seat of the diocese of Nardò-Gallipoli. The present cathedral probably stands on the site of a Byzantine church. In 1080, a church was built here by the conquering Normans, which was elevated to the status of a cathedral in the early 15th century.
The building has undergone a number of refurbishments. The present façade dates to 1710–1725. The interior contains both medieval frescoes and 19th-century frescoes by Cesare Maccari.
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.