The basilica dates from the 6C, making it the region's first example of early Christian architecture. It was built on the site of the Martyrium of Saturno, who was an inhabitant of Cagliari, and the central body of the original edifice remains: four pillars joined to arches supporting the dome, and vestiges of the little quadrangular apse. The monastery was rebuilt between 1082 and 1119 (note the final arm with three naves and the front building), and remained intact until 1669, when the basilica was demolished with a view to remodelling the cathedral.