The story
Take a moment to stand here in the heart of the Peristyle, the central courtyard of Diocletian’s Palace. As you look around, you are standing in what was once the private entrance to the imperial quarters. But your eyes are likely drawn to the most imposing structure on the eastern side of the square—an ancient, octagonal building surrounded by a forest of Corinthian columns.
This is the Cathedral of Saint Domnius, and it holds one of the most delicious ironies in all of human history. When this structure was completed around the year 305, it wasn't a church. It was the private mausoleum of the Roman Emperor Diocletian.
Diocletian was a man of immense power and ego, the only emperor to ever voluntarily retire from his post. He built this massive palace as his retirement home, and he intended for this octagonal tomb to be his final, glorious resting place. To guard it, he brought several black granite sphinxes from Egypt, one of which you can still see sitting right there, nearly 3,500 years old, silently watching the crowds.
However, Diocletian is remembered for something else: he was the architect of the Great Persecution, the last and bloodiest attempt by the Roman Empire to completely erase Christianity. He ordered scriptures burned, churches leveled, and Christians executed. One of those victims was Domnius, the Bishop of the nearby city of Salona, who was beheaded on the Emperor’s orders in the year 304.
Now, look up at the bell tower and the heavy stone walls. History has a way of flipping the script. By the 7th century, the Roman Empire had collapsed, and the very people Diocletian tried to eliminate had moved into his palace.
In a move of staggering symbolic weight, the locals cleared out the Emperor’s remains. No one knows exactly what happened to his sarcophagus or his body; they simply vanished into the dust of time. In their place, they brought the bones of the martyr Domnius and placed them inside the Emperor’s own tomb.
The hunter’s mausoleum became the martyr’s cathedral. As you walk closer, look at the frieze high up on the interior walls. You can still see the carved faces of Diocletian and his wife, Prisca, peering down from the stone.
For over a millennium, the man who tried to destroy the faith has been forced to "watch" from the walls as the city celebrates the very saint he executed. It remains the oldest cathedral building in the world that has stayed in its original structure—a Roman tomb turned into a Christian sanctuary, where the echoes of an empire are drowned out by the ringing of the bells.