The historic City of Split is the second largest in Croatia and the largest city of the region of Dalmatia. It lies on the eastern shore of the Adriatic Sea, centred on the Roman Palace of the Emperor Diocletian. Although it reached its peak during the Roman Era, it was founded as the Greek colony of Aspalathos in the 4th century BC, about 2,400 years ago. Its scenic heart is the walled Old Town, built around the Imperial Palace (305 CE). Conquered by Greek, Romans, Byzantines, Venice, Napoleon, the Hapsburgs of Austria Hungary, Nazi Germany and many others, its rich history features strongly in its diverse architecture, ruins and buildings. The Cathedral of Saint Domnius is the Catholic cathedral in Split, Croatia and the seat of the Archdiocese of Split-Makarska, The Cathedral was based on an Imperial Roman mausoleum, with a 12th Century bell tower added subsequently. Consecrated at the turn of the 7th century AD, it is reputed to be the oldest Catholic cathedral in the world that remains in use in its original structure.