From Wikipedia: https://en.wikipedia.org/wiki/Cathedral_of_Saint_Domnius

The Cathedral of Saint Domnius (Croatian: Katedrala Svetog Duje), known locally as the Sveti Dujam or colloquially 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.