The Cathedral of Saint Domnius (Katedrala Svetog Duje), known locally as the Saint Dujam (Sveti Dujam) or colloquially Saint Duje (Sveti Duje), is the Catholic cathedral in Split, Croatia. The cathedral is the seat of the Archdiocese of Split-Makarska, headed by Archbishop Marin Barišić. The Cathedral of St. Domnius is a complex of a church, formed from an Imperial Roman mausoleum, with a bell tower; strictly the church is dedicated to the Virgin Mary, and the bell tower to Saint Domnius. Together they form the Cathedral of St. Domnius.The Cathedral of Saint Domnius, consecrated at the turn of the 7th century AD, is regarded as the oldest Catholic cathedral in the world that remains in use in its original structure, without near-complete renovation at a later date (though the bell tower dates from the 12th century). The structure itself, built in AD 305 as the Mausoleum of Diocletian, is the second oldest structure used by any Christian Cathedral.NameThe cathedral was named after Saint Domnius (Saint Dujam, or Saint Domnius) patron saint of Split, who was a 3rd-century Bishop of Salona. Salona was a large Roman city serving as capital of the Province of Dalmatia. Today it is located near the city of Solin in Croatia. Saint Domnius was martyred with seven other Christians in the persecutions of the Emperor Diocletian. He was born in Antioch, in modern-day Turkey, and beheaded in 304 at Salona.