Castellaneta Cathedral is dedicated to the Assumption of the Virgin Mary. It is the episcopal seat of the Diocese of Castellaneta. The first cathedral on the site was initially dedicated to Saint Nicholas of Bari, and dated at the latest from the Norman occupation of the last decades of the 11th century. In the 14th century, it was replaced with a Romanesque structure with a basilica layout of a central nave and two aisles separated by columns, all three terminating in semicircular apses. The dedication was changed at this time to the Assumption of the Virgin Mary.
Three chapels were later added: the Chapel of the Most Holy Sacrament (Santissimo Sacramento) in 1538 and the Chapel of Mary the Consoler (Santa Maria Consolatrice) in 1643, both founded by confraternities; and the Chapel of the Most Holy Crucifix (Santissimo Crocifisso). There is also a chapel dedicated to Saint Nicholas, with Romanesque capitals. In 1771, a new white limestone façade was added. Today, the bell-tower retains some of the Romanesque-Gothic elements. In the 18th century, new polychrome altars were built. The Bishop's Palace is adjacent.
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.