Basilica di San Giovanni

According to Roman law, Christians were not allowed to bury their dead within the city limits (which during the Roman occupation did not extend beyond Ortygia). Forced to go elsewhere, Christians conducted their burials in the outlying district of Tyche and its underground aqueducts, unused since Greek times. New tunnels were carved out and the result was a labyrinthine network of burial chambers, most of which are inaccessible except the ones underneath the Basilica di San Giovanni.

The church itself is pretty, with its skeletal rose window open to the sun. In the 17th century it served as the city's cathedral and is dedicated to the city's first bishop, St Marcian, who was tied to one of its pillars and flogged to death in 254.

The catacombs here are, for the most part, dank and a little spooky. Thousands of little niches line the walls and tunnels lead off from the main chamber (decumanus maximus) into rotonde, round chambers used by the faithful for praying. All of the treasures that accompanied the dead on their spiritual journey fell victim to tomb robbers over the centuries bar one: a sarcophagus unearthed in 1872 and now on exhibition in the Museo Archeologico Paolo Orsi.