Thanks to its favorable position between the sea and a fertile plain surrounded by two swamps that cut it off from the inner lands of Sardinia, Cagliari has been inhabited since prehistoric times. Established around the seventh century BCE as part of a string of Phoenician colonies across the island the city was first known as Karalis and was an important port at the time for trade with Africa. And it was due to this opportune positioning that made it such a valuable prize. By 238 BCE the island had already been conquered by the Carthage Empire and would again change hands with their defeat by the Romans. Karalis would even serve as the headquarters for the Second Punic War and the chief naval station on the island. During the civil war between Julius Caesar and Pompey the city was one of the first to declare in favor of the former, and would be the only one to offer any resistance when the island fell a few years later to Pompey’s son during the Second Triumvirate. While it would continue to be regarded as the capital of the island, and it did not become a colony, the inhabitants did obtain the rights of Roman citizens. With the rise of Christianity in the empire a Christian community would find its way to Karalis some time during the third century, which by the century’s end would see a bishop installed. Interestingly the fourth century bishop Lucifer would come to power here and go on to develop the Luciferian heresy that would lead to his desert banishment by Emperor Constantius.

Unfortunately the fall of the Western Roman Empire resulted in the island falling into the hands of the Vandals, and then again to the Byzantine Empire, before going on to become an independent kingdom, but had to be deserted for some time thanks to its exposure of attacks from the sea by Moorish pirates.