The Cellars of Diocletian's Palace - Credit: Wikimedia Commons
The Cellars of Diocletian's Palace, sometimes referred to as the "basement halls", is a set of substructures, located at the southern end of Diocletian's Palace (now the southernmost part of Split Stari grade), that once held up the private apartments of Emperor Diocletian and represent one of the best preserved ancient complexes of their kind in the world. Read more on Wikipedia
Source: en.wikipedia.org