The basilicas are surrounded by cemeteries, which are full of coffins, all of stone and covered with mosaics. The basilica of St. Salsa, which has been excavated by Stéphane Gsell, consists of a nave and two aisles, and still contains a mosaic. The Great Basilica served for centuries as a quarry, but it is still possible to make out the plan of the building, which was divided into seven aisles. Under the foundations of the church are tombs hewn out of the solid rock. Of these one is circular, with a diameter of 18 m and space for 24 coffins.