The basilica is probably the most ancient example of Romanesque architecture in Cagliari. A 6th century document mentions the site for the first time. It had probably already been built in the place where young Saturnin had been martyred in 304 AD. The church and the adjacent monastery were gradually abandoned during the Middle Ages, then restored during the Spanish domination, before part of its limestone bricks were used for restoration works in the Cathedral. The surrounding necropolis has given light to many Roman and Byzantine burials. Only the central part of what used to be the Greek cross plan is visible.