Known locally as the Sveti Dujam or colloquially Sveti Duje, this cathedral finds its seat in the oldest building in Split – the Mausoleum of the Roman Emperor Diocletian. 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. It was consecrated at the turn of 7th century AD, and today is regarded as the oldest Catholic cathedral in the world that remains in use in its original structure (but the bell tower dates back to 12th century). Saint Domnius is patron saint of Split. He was a bishop of Salona in 3rd century. Saint Domnius was martyred with seven other Christians in the persecutions of the Emperor Diocletian.