The basements of Diocletian's Palace are called covered and partly underground areas in the southernmost part of the Old Town of Split. It is about oversized, larger or smaller halls and corridors between them. Their surface is as large as eighth of the entire palace. In time they were almost overwhelmed, but the awareness of their existence in Split was permanent and, with fear and devotion, they perceived the dungeons in which the Emperor Diocletian tortured Christians. But some more affluent Splinchians who had houses above them sometimes beat their vaults and redesigned them into their own storerooms - basement spaces.

Their digging began in the 19th century, and the greatest momentum was in the 1950s and so far, they are mostly discovered. Cellars are today used as an attractive fair and exhibition space.