Most of what is now Split’s historic center was once the palace of Roman emperor Diocletian, surrounded by thick stone walls. What is now the Church of St. Martin was then a passageway for the walls’ guards. His rule lasted from 284 to 305, and was partly known for the Diocleniatic Persecution, an official and bloody attempt to remove Christianity from the Empire (before Emperor Constantine made it the preferred religion in 324, a little over a decade after Diocletian’s death). As the only emperor to have voluntarily abdicated (due…