Faith and mystery seep from its pure white stones, that cry out the tragic story of the young Saturnino (Saturno in some sources), who was decapitated in 304 AD for refusing to deny his Christian faith. The basilica where the martyr, who is the patron saint of Cagliari, was buried still has its original appearance of a martyrium. This is the oldest church in the capital, built in Byzantine-Proto-Romanic style between the 5th and 6th century: together with the necropolis on which it was built, it is one of the most important paleo-Christian complexes in the Mediterranean. Excavations have found Roman and Byzantine burials, and you'll be amazed by the size of the cemetery.
The ancient building is laid out in the form of a Greek cross, with four equal-length arms and a central body topped with a dome, which remains intact together with the remains of the apse. After sinking into the quiet inside, you can admire the finesse of the external decorations on the central nave, along with the only remaining Romanic door on the eastern wing, with a late-Romanic arch.