The Carlo al Corso church replaced an earlier church. This church likely designed by Rosario Gagliardi, was part of the town reconstruction after the 1693 Sicily earthquake.
The concave façade has three superimposed orders of columns, identified by their capitals from base to roofline as Doric, Ionic and Corinthian; in the progression expected in classical construction. The third story has floral oculus. The interior has a longitudinal layout with a barrel vault sustained by pilasters. The main altar was rescued from the prior church.
Inside the church, the 18th-century altarpieces display a Sacrifice of Isaac; a Flight into Egypt; a Deposition; San Carlo Borromeo ministering to those ill with the plague; a Virgin and Child with saints; Biblical Scene; St Ignatius of Loyola, founder of the Jesuit order; and wood icon of St Aloyitius Gonzaga, another Jesuit saint. The main altar is flanked by marble statues symbolizing Faith and Hope respectively, sculpted by Giuseppe Giuliano. The nave ceiling is frescoed by Costantino Carasi, depicting the Transfiguration and the Healing of the Paralytic, with a central panel depicting the Triumph of the Agnus Dei. The spandrels that support the dome are frescoed with the evangelists, and just below are four allegorical statues depicting the respective cardinal virtues.
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.