The Catacombs of San Callisto (St. Calixtus) and San Sebastiano, both underground burial places in the Via Appia Antica, are extensive - San Callista fills an area of 300 by 400 meters -- with intricate multi-layered networks of passages and chambers carved into the soft tufa.
In addition to the tombs, St. Calixtus has six sacramental chapels, constructed between 290 and 310, with both pagan and early Christian wall paintings. In the Papal Crypt are the tombs of most of the martyred Popes of the third century identified by Greek inscriptions.
San Sebastiano, one of Rome's seven pilgrimage churches, was built in the fourth century on the site of old cemeteries and catacombs that, along with the foundations of a Constantinian basilica, can be explored.
Tomb chambers are on several levels with fine paintings, stucco decoration, and inscriptions dating to the first century AD. Although venerated remains are thought to have been brought here for safekeeping during persecutions, these were cemeteries, not hiding places for Christians.
