The site was originally called 'ad catacumbas' or, according to the most common explanation, 'near the quarry', due to the presence of ancient pozzolana quarries. Through habitual usage, this place name was then used to mean the Christian underground cemeteries, known today as catacombs. As often happened in ancient times, the quarry was adapted by Christians into the cemetery, with modest burial places such as loculi and arcosoli.
The Christian community, given the large number of its members, the inumation process and the high cost of suburban land, continued to dig the tuff quarry to form a network of 12 km of underground tunnels divided into three levels. Before the advent of Christianity the Romans  called their burial places "nekropolis", a Greek word meaning city of the dead.
The first Christians, on the other hand, preferred to call their burial grounds 'cemetery', from the Greek 'koimào' which means 'to sleep'. Along the underground galleries you will notice the great variety of tombs and decorations. Each tomb had its own small mark to be recognized, such as an object or a simple fragment of a lamp, a coin, a cup bottom, jewelry, or a child's toy.
In many cases, a name scratched on the closing mortar has handed down to us the memory of the deceased. The burial of the martyr Sebastian was a fundamental event for the development and notoriety of the catacomb, and the veneration of this witness of God caused profound changes within the catacomb. Thanks to his presence, places near his venerated tomb were increasingly sought out.


Towards the mid 3rd century A.D., the topography of the place was literally upended. The 'Piazzuola' was completely filled in and a courtyard was created above the mausoleums. At that time, the 'triclia' was created, which was a covered environment accessible by a small staircase, and consisting of a large porticoed room surrounded by a bench on three walls.
Many scholars believe that, precisely in this period, this complex temporarily housed the remains of the apostles and martyrs Peter and Paul. Moreover, it came to be called the 'Memoria Apostolorum', and on the back wall many graffiti were found with invocations and prayers addressed to Peter and Paul, testimonies of the profound veneration of the two saints.
Some of these interesting, evocative graffiti are still visible, such as the one of a certain pilgrim who wrote: 'Paule et Petre petite pro Victore', request for intercession addressed to the two most important martyrs of Christianity.