Originally built as Emperor Diocletian’s mausoleum in the 4th century, this structure was transformed into a cathedral in the 7th century—making it the oldest Catholic cathedral still in use within its original building. Its octagonal core, once a symbol of imperial power, now honors Saint Domnius, the patron saint of Split, whose remains were placed here in a striking reversal of history. The cathedral’s bell tower, rising 57 meters above the city, blends Romanesque, Gothic, and Renaissance styles and took centuries to complete. Inside, Roman stonework meets Christian altars, with intricate carvings and relics that span empires and faiths. It’s not just a place of worship—it’s a layered narrative of resistance, transformation, and cultural continuity.