CATACOMBS, CEMETERY IN. - From the Greek κατὰ κόμβας, it was originally a topographic term used to designate the hollow of the Appian Way between the second and third mile, and precisely between the present church of St. Sebastian and the tomb of Cecilia Metella. The designation is clearly attested in the Chronographer of 354 under the Depositio martyrum on 20 January and 29 June, where St. Sebastian and St. Peter are respectively commemorated, and in the Chronica Urbis Romae for the circus dedicated by Maxentius in 309 in honor of his son Romulus.
In this area is found one of the most important and complex monumental groups of subterranean Christian Rome; it has been the object of numerous studies, especially from 1915 onward, when the Memoria Apostolorum came to light. The monuments composing it range from the 1st to the 4th century A.D. At the original level of the hollow, the remains of a private road that crossed the Appian Way are still visible: on the north side of it stood a two-story private house and other buildings very probably connected with funerary cult. Two series of columbaria were in fact built on the same side of the road: in one of those closest to it, an inscription still in situ of a freedman of Vespasian clearly proves it to be of the 1st century, while those of the other series are considerably later. In the latter, however, there are also Christian elements (paintings and inscriptions) from the first half of the 3rd century: a sign that the owners had embraced the new faith.
Around the middle of the 3rd century, a partial filling-in of the hollow was carried out and a kind of trapezoidal courtyard with a sloping floor was built: the so-called Triclia. It was certainly a place of Christian gatherings, since the walls of this courtyard are full of graffiti which, besides the rite of refreshment, promises or fulfillments of vows, refer almost unanimously in Greek or Latin to prayers addressed to the apostles Peter and Paul. The discovery of these graffiti was made in 1915, and the monument was commonly called the Memoria Apostolorum. On the nature and purpose of the Memoria, however, scholars' opinions differ. Ancient literary traditions (Liber Pontificalis, Martyrologium Hieronymianum, Itineraries, Passiones) all allude to a temporary burial of the apostles Peter and Paul in the C.; no one, however, has determined the site more specifically, nor have the excavations revealed anything positive and definitive. The study of the literary sources has divided the authors into three groups: 1st, the Memoria is a true burial monument originating from the temporary interment of the bodies of the apostles Peter and Paul, either immediately after their martyrdom and before their definitive placement at the Vatican and on the Via Ostiense, or in 258 during the persecution of Valerian; 2nd, the Memoria was built to commemorate the dwelling of the two Apostles while alive in one of the houses in the C.; 3rd, the Memoria arose in connection with the institution of a liturgical feast in honor of the two Apostles in the C., begun in 258, when, because of the persecution of Valerian, Christians were forbidden entry into the cemeteries and therefore could not venerate the tombs of the Apostles in their respective places.
In the first half of the 4th century, a new and more extensive filling-in was carried out: all the pre-existing monuments, pagan and Christian, were sacrificed for the construction of the grandiose basilica Apostolorum, as it was called from the beginning. In its original structure this presented an architectural form unique in the Christian basilical tradition: the side aisles, in fact, rather than by columns, were separated by brick piers that formed almost an ambulatory at the end of the apse. It seems that the basilica was intended as a burial place; around the perimeter walls, in fact, numerous mausoleums were opened. The most important of these is the one placed to the left of the apse, commonly called the Platonia, in which Pope Damasus placed a poem of his, and, in the 5th century, the body of the martyr Quirinus of Siscia was transferred following the invasion of Pannonia by the barbarians.
Before the construction of the basilica, however, an underground cemetery had begun in the C., in which were buried the martyrs Eutychius, to whom Pope Damasus dedicated a poem, and Sebastian, whose tomb was subsequently arranged with a crypt with a double staircase to the left of the basilica. The presence of these two martyrs was certainly the cause of the cemetery's development in the 3rd and 4th centuries, and the cult paid to St. Sebastian led to the designation by his name of both the cemetery and the basilica.