From the beginning of the 4th century for about 80 years, the pagan worship of the goddess Dia and the Christian one of the Portuensian Martyrs coexisted, with the temple of the goddess Dia at a very short distance from the Catacomb of Generosa. Possibly the latter prevailed over the former, anyway without completely replacing it.
In 382 AD, the immunitas (immunity), which according to Roman law sanctioned the untouchability of pagan places of worship, was repealed. The sacred trees dedicated to the goddess Dia in the inviolable sacred grove were cut down to make room for new Christian buildings. After edicts were promulged to legalize above-ground burials, the Catacomb of Generosa was not used anymore and the surrounding area was transformed into a Christian sanctuary with the construction of the so-called Damasian Basilica or Damasian Oratory, named after Damasus (366 – 384 AD), the Pope who commissioned it.
In 1868, it was rediscovered by the famous Christian archaeologist Giovanni Battista De Rossi, along with the Catacombs of Generosa, and partially excavated. While sifting through the soil excavated around the apse, De Rossi found a block of marble with the inscription “-stino Viatrici” featuring the characteristic curlycue letters known as Filocalian or Damasian, named after Filocalus, a calligrapher who, in the 4th century on behalf of Pope Damasus, decorated the tombs of the martyrs with epigraphs marking their presence. By studying the martyrologies (lists and biographical notes of saints), De Rossi understood that on that block was a part of an inscription with the names of 2 of the 4 Portuensian Martyrs, Faustinus and Viatrix (later transformed into Beatrix due to an etymological shift), in the dative case, and he completed it as follows: “Sanctis Martyribus Simplicio Fau|stino Viatrici | et Rufiniano Damasus Episcopus fecit” (Pope Damasus erected this oratory for the Holy Martyrs Simplicius, Faustinus, Beatrix, and Rufinianus). The marble fragment, now displayed inside the Catacomb of Generosa, belonged to the architrave (header) of the basilica’s façade, on which the dedication to the martyrs was inscribed. The team of French scholars who investigated the area in the 1970s found it along the long wall facing east, which means that instead of on the short side as in other basilicas, the entrance was evidently on the long side.
The basilica, carved into the rock (semi-hypogeum), was built cutting off a section of the hill above the catacomb, which had to be reinforced to support its weight. The interior was divided into three naves with an apse that, instead of being in line with the long axis, corresponds to the burial place of the martyrs, and is therefore decentralized and slightly oblique. From the apse, it was possible to enter directly the Martyrs’ tomb through a small door, the introitus ad martyres (entrance to the martyrs). Next to it was the fenestella confessionis (confession’s window), through which the martyrs’ crypt could be viewed. People put pieces of cloth (brandea) through the window and thought that by coming into contact with the sacred burial, they could themselves be considered relics. Being buried close to the martyrs’ tombs was highly requested, so that tombs were placed under the oratory floor until the beginning of the 6th century. Raids and instability convinced Pope Leo II, as recorded in the Liber Pontificalis (a record of the biographies of the popes), to close Christian houses of worship in the Roman countryside and move the relics from there to churches within the walls, to defend and preserve them.
Between the end of the 6th century and the beginning of the 7th, the oratory was abandoned, and it was rediscovered only in 1868 by Wilhelm Henzen, the then secretary of the Institute of Archaeological Correspondence. Henzen was looking for epigraphs of the acta Arvalium, the records of the rites that the Arval Brothers held during the festivals in honor of the goddess Dia and which they inscribed on the walls of her temple. Once he reached the top of the hill, called Monte delle Piche in the modern era, the scholar realized that instead of fragments of the Arvalian slabs, on the ground were fragments of Christian inscriptions. Giovanni Battista De Rossi, topographer of the Pontifical Commission of Sacred Archaeology, famous for having established the new discipline of Christian archaeology, was thus informed. He supervised the first archaeological investigations, but after finding the catacomb beneath the basilica, he focused his attention on the cemetery area, where there were still 800 intact tombs in 400 meters of galleries. New excavations by the Pontifical Commission of Archaeology together with the École française de Rome, directed by Philippe Pergola, date back to 1980-86, when the entrance was found and the surface area was estimated to be about 300 square meters wide. While De Rossi thought it was a small country church (20 meters long and 14 meters wide), the oratory turned out to be a medium-sized basilica (with a surface of the naves 280 square meters wide).
Reference Bibliography:
E. Venditti, Le Catacombe di Generosa alla Magliana, Roma 2000