Emperor Diocletian (a.d. 245–316) commissioned construction of his palace in a.d. 293 as an imperial retirement home, to which he retreated upon abdicating in a.d. 305. He probably chose this location for its proximity to his birthplace, Salona, and for its natural beauty, between sea and mountains. Built of local limestone (largely from the nearby island of Brač), the vast palace covers almost 3 hectares (10 acres), with walls that are at least 2m (6 ft.) thick and up to 30m (100 ft.) high in parts. Inside were Diocletian’s private apartments, overlooking the sea, several temples in the central public area close to the Peristil, plus accommodation for soldiers and servants on the land-facing side. In the early 7th century, refugees from Salona took shelter here when the Avars and Slavs attacked and destroyed their city, and soon started turning the palace into a settlement in its own right. Through the centuries, building spread beyond the palace walls, and various rulers and peoples, most notably the Venetians, built structures within and around the complex, adding to its fascinating and unique character. The entire old town is now a UNESCO World Heritage Site.