Diocletian was quite a character.

This Son of Jupiter thought it politically expedient to kill Christians, but was particularly wary of his potential future. Since he knew that the Roman emperors before him commonly ended their reigns in a particularly unsettling manner -- assassination -- our guy decided that he'd rather retire, the first Roman Emperor to do so. In 295, a good ten years before retirement, he started building his retirement palace in Split, now a Unesco World Heritage site. Finished in 305 and considered one of the most imposing Roman ruins in existence, the harbor-facing palace was built from lustrous white stone from the Croatian island of Brac. The highest walls measure 26 meters, and the entire structure covers 31,000 square meters. There are now quaint and chic shops intermixed throughout and within ancient buildings. Three thousand people live inside the walls, but if you close one eye to this, and open the other to what was... there you are, gladiator, sword in hand as the lion leaps for your throat.