Beneath the vineyards and villas in the environs of Rome lie catacombs, some discovered and then lost, some still preserved, and certainly others yet to be revealed.
Down through the centuries, the discovery of these subterranean sites has been effected through happenstance, such as laborers digging quarries or shoring up the foundations of buildings, through curiosity and interest of would-be explorers and devout Christians, or through scientific investigations by scholars and archaeologists in the course of excavation.
By and large, only the sanctuaries (and this the adjoining catacombs) of S. Lorenzo (catacomb of Cyriaca) on the via Tiburtina, S. Pancrazio on the via Aurelia, and S. Valentino on the via Flaminia were still visited for reasons other than that of vandalism for tomb robbing and the recycling of ancient building materials. The catacombs of S. Sebastiano also in part remained accessible, but, from a confusion in topographical designation, they were commonly known as those of S. Callisto, along with other cemeteries along the Appian Way.
It was not until the 15th century that some of the catacombs at Rome were rescued from the obscurity of the Middle Ages by the visits of pilgrims and by reawakened humanistic interest.
The pre-eminent nineteenth-century scholar of these sites, Giovanni Battista de Rossi, notes as an early visitor a certain Johannes Lonck (1432), who wrote is name on the walls of a cubiculum in the catacombs of Callisto. Shortly thereafter, some frates minores (friars minor, or Franciscan brothers), made several visits to this site, as did some Scots in 1467. Fifteenth century academicians such as members of the Accademia Romana, led by their flamboyant "pontifex maximus" (the title of a pagan priesthood later used by the Pope), Pomponius Letus, assisted by Pantagathus, sacerdos, came to the catacombs with different intentions. The Accademia Romana wished to broaden their knowledge of Classical antiquity by searching for pagan monuments, and referred to its members as unanimes antiquitatis amatores or unanimes perscrutatores antiquitatis. Pope Paul II was affronted by their actions, no doubt perceiving their attitude and activities as a threat to his Christian authority (1. G .B. de Rossi, Roma Sotterranea, 1, pp. 2-9; Testini, Catacombe cristiane, p. 15). The pope had good reason to suspect academy members of irreverence: the Perscrutatores, in fact, were descending like "modern pagans" into the catacombs of Callisto, Ss. Marcellino e Pietro, Pretestato, and Priscilla, where they wrote upon the ancient walls of chambers their assumed names and titles (P. Testini, Catacombe cristiane, pp. 15-16). In the end, the group was prosecuted by the local ecclesiastical authorities, but the publicity surrounding their excursions served to rekindle awareness of the existence of the catacombs and provoke visits by others.
Religiously-oriented investigation is first documented on an extensive basis by Onofrius Panvinius (1529-1568), who conducted organized and methodological study of the Christian cemeteries of every region of the ancient world, but especially those of Rome, though the work was based almost entirely on mention of the sites in historical, ecclesiastical, and epigraphical sources, and not specific site knowledge. His work on the subject, De Ritu