Along with the Catacombs of Santa Lucia, those of San Giovanni make up the part that is easiest to visit in the whole complex of Syracuse's catacombs, which in terms of expansiveness and articulation are second only to those of Rome.
The atmosphere that permeates this underground place is extraordinary, full of charm and mystery. 

This catacomb was excavated for the most part between 315 and 360 A.D., and remained in use until the end of the 5th century.

Contrary to popular belief, burial in catacombs (or in underground tunnels carved into rock) was not an exclusively Christian custom, so much so that in Syracuse in the Catacomb of Vigna Cassia (open for visits by appointment only and only in large groups) the graves of dead Christians and pagans are located side by side, apparently linked by ties of kinship and not of religion. 

In fact, in Rome there are Jewish catacombs and pagan catacombs in addition to the better known Christian catacombs.

To save work, the tunnels in the Catacomb of San Giovanni of Syracuse were opened initially following the route of a disused Greek aqueduct (some traces of which are recognizable on the ceiling of the main gallery), which was expanded to its current dimensions. 
Similarly, some existing cisterns along the route were converted into funeral chapels for families of distinction.

This underground cemetery was built as mass burial ground even for the poorer members of the population. The rock, which was easy to work with, made it possible to create, here and in other Syracusan catacombs, a very particular type of "serial" burial, called by archaeologists "polysome arcosolium". These are very long niches in the walls, as wide as a human body and tall enough to be able to insert a corpse, in which a first body was entombed with a stone slab, after which in the new space thus created a second corpse was entombed and sealed by another slab, and so forth. 
In these "tunnel-graves" of almost industrial composition it was possible to lay as many as 30 corpses side by side.
When the space available in this catacomb was exhausted, they proceeded as best they could, employing every corner that remained free, on the walls and even on the floor, also invading the cisterns / chapels, one of which survives filled with the sarcophagi of a group of nuns from the Byzantine period. 

It is not difficult for us to imagine the thousands of people who for centuries walked through those tunnels to bring a greeting to a loved one who had passed away. The holes in some surviving tombstones reveal that in this place of Christian burial an ancient pagan ritual survived, the refrigerium, which consisted of pouring through these openings to the deceased, on the anniversary of his or her death, a little wine, milk and honey.

Unfortunately, after thousands of years of looting, what survives is only the "bare bones" of the building, stripped of colored plaster, mosaics, stone slabs (which must have decorated at least the tombs of the richest), and even small objects that were incorporated into the enclosures to distinguish one tomb from another other. The guide on a tour will illuminate and describe some frescoes and inscriptions that have miraculously survived so much hardship, which will make even more regrettable what has been lost.

The few crumbs that escaped the treasure hunters (they even took marble to burn for making lime) were recovered by archaeologists in the present era, and are now in the Archaeological Museum "Paolo Orsi". 
Of note above all, a splendid sarcophagus (richly decorated with biblical scenes in bas-relief) of an aristocratic lady, Adelfia, survived only because it was hidden in grave dug into the ground and filled with earth.

From the Catacombs of San Giovanni it is easy to reach the Regional Archaeological Museum, the Papyrus Museum, the Shrine of the Madonna delle Lacrime, and a little further away, the Archaeological Park in Syracuse.