Diocletian's Palace was built around the year 300 AD, more than 1,700 years ago. It covered about 3 hectares - roughly the size of three football pitches - and had thick walls, towers, a grand courtyard and hundreds of rooms. Diocletian lived there for the last nine years of his life.
The palace was so well built that when the empire declined, the stone walls were simply too solid to demolish. People moved in and adapted the rooms. A temple became a cathedral. A mausoleum became a bell tower. Underground vaults that stored the palace's supplies became basement shops and galleries. Layer after layer of history piled on top of each other.
Today you can walk from a modern café straight into a 1,700-year-old Roman basement, with the original stone columns still standing. The peristyle - the grand open courtyard - is now used as an open-air concert venue in summer. Children play in the alleys that were once Roman corridors.
Archaeologists are still finding new things. The palace is so large and so densely inhabited that full excavation is almost impossible - there are apartments on top of Roman rooms on top of even older buildings. It is like a layer cake of history.