Rome in the Footsteps of an XVIIIth Century Traveller

Few ancient monuments that have come to light of recent years have aroused so lively an interest amongst scholars or so widespread a curiosity in the general public as the subterranean building of basilican plan discovered in 1917 as if by chance near the Porta Maggiore in Rome. Its situation at a depth of 50 feet below the present level of the soil, the curious mode of its construction, the secrecy of its approach, the mystical character of its decoration led to the theory, put forward almost from the first, that this was probably the secret meeting-place of some religious pagan fraternity.
Abstract from "The Stuccoes of the Underground Basilica ..." - The Journal of Hellenic Studies - 1924
In April of 1917, the enlargement of the railway lines leading to Stazione Termini just outside Porta Maggiore on the Via Praenestina was halted by a cave-in. The cause turned out to be the collapse of an ancient roof of a building nobody knew was under their feet. As it happens, most ancient Romans probably had no idea it was under their feet either. It was deliberately built about seven or eight meters (23-26 feet) below the level of the ancient Via Praenestina in the early Ist century AD and constructed in such a way as to give little indication that something was going on down there. The part that caved in was the barrel vaulted roof of a long entrance gallery that sloped down from the surface to a small square vestibule.

Vestibule: ceiling with the only light and air source (which has the shape of the hall)

Light and air came down a shaft to the vestibule, but the inner recesses of the basilical space must have been lit by lamps. The decoration of the vestibule is dated earlier than that of the hall, although the construction process was completed at the same time. It is one of the most fascinating aspects of this unique structure. Builders dug seven or eight meters down into the soft volcanic tufa creating trenches where the perimeter walls would go and squared pits where the pillars would go. They then poured a mixture of pozzolana, flints and other stones into the trenches and pits and let it set. Once it had hardened, they completed the arches over the pillars and the barrel vaulted ceilings. Lastly they dug out all the material from the interior. The process was basically that which was used for the construction of underground cisterns.

Vestibule: (left) floor mosaic and faded stucco decoration of the wall; (right) paintings on red background in the lower part of the wall

To provide access to the structure which is now 13 meters below street level, a staircase was built from the Via Praenestina connecting to the entrance gallery right before it opens into the vestibule. The decoration of the vestibule did not particularly impress the archaeologists; other buildings of the early Ist century AD, e.g. Villa Romana della Farnesina had a finer and more complex decoration. The depiction of birds, ships, trees, etc. brings to mind some paintings at Pompeii and the underground location of the basilica recalls that of Domus Aurea with its vanishing frescoes.

Vestibule: detail of the ceiling

The elaborate decoration of the ceiling of the vestibule is characterized by the use of colour. One of the stuccoes depicts a maenad, a female follower of Dionysus/Bacchus next to a panther, the animal sacred to the god. Thiasi, scenes referring to Dionysus/Bacchus are very often seen in Roman sarcophagi, and the maenad in the vestibule together with other elements of the decoration of the building could suggest that the basilica had a funerary purpose, perhaps the site where the family of the dead periodically met for the celebration of remembrance rites. Because no cinerary urns or sarcophagi were found at the site nor there is evidence of containers/spaces where they could be placed, the actual tombs must have been in the proximity of the basilica.

Basilica: (left) seen from the vestibule: an untiled area in the floor suggests that an altar or the base of a statue was removed when the site was closed: (right) apse and pillars

It's an odd feeling, standing in a church that isn't a church, four miles from the Vatican. We're in the nave of the basilica, flanked by two side aisles. The roof is vaulted, the atmosphere respectfully hushed. "So it's a basilica, but not a church?" I ask. "Correct," says my guide. (..) As we descend the 44 stairs (..) I'm expecting the worst. And then we step inside an interior so clean it seems to glow in the lamplight. It's not my imagination; my guide explains the stucco used was laced with mother of pearl, so the walls are pearlescent. Nobody knows what went on here. (..) The Romans, who documented their empire in meticulous detail, never mentioned this place of worship or meeting house, as it's thought to be. It was wiped from history.
Julia Buckley - National Geographic UK - 2018
The architecture follows an east-west orientation; the vestibule opens into a rectangular hall 12 meters (40 feet) long and nine meters (30 feet) wide divided into three barrel-vaulted sections. Two rows of three square pillars separate the central nave from the aisles on either side. The nave is wider than the aisles and opens into a semi-circular apse at the end.

Plate depicting the apse stucco from "Arthur Bernard Cook - Zeus. A Study in Ancient Religion - 1940"

The magnificent stucco-relief, which fills the semidome of the subterranean basilica outside the Porta Maggiore at Rome. (..) Before us lies a stormy sea with threatening breakers. A rock-bound coast looms up on either hand. From the headland on the right, where a tree is growing, a veiled woman with a lyre steps down towards the water, attended by Eros. In front of her a Triton, or perhaps rather a personification of the Wind, holds a mantle to serve as her ferry- boat across the flood (today it is identified as Leucothea, a sea-goddess). On the cliff to the left sits a man, who leans his head on his hand in an attitude of deep dejection. In front of him a second and unmistakable Triton turns away, blowing a blast on his horn. Finally, in the distance is seen a rocky island, on which stands Apollon holding out his hand as if to welcome the woman. Francesco Fornari, one of the two scholars first privileged to publish this wonderful composition, saw at once that the subject must be the last voyage of the soul over the waters of death to the Islands of the Blest. Much has been written on the relief since then and, though various points of content and style remain uncertain, it is now generally admitted that the whole design illustrates the entrance of the soul into the Otherworld as conceived by some Pythagorean sect in the middle of the first century A.D. (..) It was suggested that the stucco portrays a well-known story, namely the famous "Leucadian Leap" of Sappho in her attempt to be freed from her hopeless love for Phaon. (..) Jérôme Carcopino, Director of the French School in Rome turned possibility into something very like certainty by pointing out that the Pythagoreans were much concerned with the myth of Sappho and Phaon.
Arthur Bernard Cook - Zeus. A Study in Ancient Religion - 1940

Stucco of the apse portraying: (right) Sappho (see an assumed portrait of the poetess) about to jump from the Leucadian rock; (left) Apollo standing on a rock; (in the lower part) Phaon, a triton and Leucothea who is ready to embrace Sappho with her mantle

Apollo on the heights watches the open sea.
(..) Seek out the Leucadian height
right away, and don't be afraid to leap from the rock!
(..) I rose,
chilled, and the tears ceased flowing from my eyes.
I'll go, oh Nymph, and seek the rock you've shown me:
let fear be far from me, conquered by frantic love.
Whatever comes will be better than what is. Breeze,
support me - indeed, my body has no great weight.
You also, sweet Love, lift me on your wings as I fall,
lest my death be charged to Leucadia's waters.
Ovid - Heroides XV - Sappho and Phaon - Translation by A. S. Kline
Whatever be thought of this catena of interpretations, it can hardly be denied that Ovid's description of Sappho and the Leap does fit the design of the relief with remarkable aptitude. The single tree overlooking the water, Apollon on his rock, the woman stepping down from the cliff, the personification of wind with a mantle for a boat, the attendant Eros, the lyre carried by the woman - almost every point in the picture can be paralleled from the poem. Cook
It is true that Pliny says nothing about the death or leap of Sappho, nothing therefore bearing on the subject of the apse stucco, yet we may now reasonably assume that the whole Sappho legend entered into Pythagorean lore, and that M. Carcopino by this timely discovery has disposed of any doubt as to the Pythagorean character of the basilica, or as to Sappho's leap being the subject of the apse stucco. The Journal of Hellenic Studies
The prevailing theory about the purpose of the building is that it was a place of worship for members of a Neopythagorean sect. Neopythagoreanism (a modern definition) was an attempt to introduce a religious element into pagan philosophy in place of what had come to be regarded as an arid formalism. The founders of the school emphasized the fundamental distinction between the Soul and the Body. The soul must be freed from its material surrounding by an ascetic habit of life. Bodily pleasures and all sensuous impulses must be abandoned as detrimental to the spiritual purity of the soul, as done by Sappho.

Ceiling: The rape of Ganymedes by a winged genius and not by Zeus (see the event in Roman mosaics) and other subjects, including heads of Medusa, which are often depicted in a funerary context

The second question archaeologists tried to answer was related to whom had built the underground basilica. An event reported by Tacitus gave them a clue:
Claudius was being forced to a display of sheer cruelty, still by the machinations of Agrippina. Statilius Taurus, whose wealth was famous, and whose gardens aroused her cupidity, she ruined with an accusation brought by Tarquitius Priscus. He had been the legate of Taurus when he was governing Africa with proconsular powers, and now on their return charged him with a few acts of malversation, but more seriously with addiction to magical superstitions. Without tolerating longer a lying accuser and an unworthy humiliation, Taurus took his own life before the verdict of the senate. Tarquitius, none the less, was expelled from the curia - a point which the Fathers, in their detestation of the informer, carried in the teeth of Agrippina's intrigues.
Tacitus - Annales - Book XII - Loeb Classical Library 1937
The Statilii Tauri had large properties (Horti Tauriani) in this part of Rome and tombs of their freedmen exist near Porta Maggiore, so it is possible that the "magical superstitions" were practiced in the secrecy of the underground basilica. After the death of Titus Statilius Taurus his heirs might have decided to close it and to remove whatever statues or altars it contained to prevent them from getting into any more trouble. It was filled with rubble and sealed just a few years after it was built.

Ceiling: The rape of one of the daughters of Leucippus by one of the Dioscuri (see the event in a Roman sarcophagus) and other scenes

On the central vault the subject-matter in the square panels is a miscellany of scenes from Greek myth or drama, the smaller rectangular panels show cult objects of various kinds, athletic games, rural life, rustic sanctuaries, pygmies; the intervening spaces are filled with palmettes, victories, erotes, tables with food and drink, candelabras. Paris and Helen, Orestes and Iphigenia, Achilles and Chiron, Jason and Medea, Heracles are some of mythological personages who are portrayed on the vault.

Left aisle and details of its stucco decoration (you may wish to see the stucco decoration of a tomb which was found along Via Portuense)

Around the upper zone of the walls is a set of figures standing on bases, presumably meant to be statues.
The archaeological importance of the basilica is not reflected in its present fame, as it has had little opportunity to be exposed to the public because of its delicate condition. Stucco is extremely susceptible to moisture and as early as 1924, just seven years after it was found, water damage became such a concern that conservators covered the top with a cap of pipe-clay to form an impermeable membrane. In 1951 a dome of reinforced concrete was built to protect the basilica from the vibrations of the trains. A new lighting system using LED lights of different colours suggest the natural illumination that bathed the basilica from the skylight of the vestibule. The right aisle is still being restored.
The image used as background for this page shows a detail of a stucco (a profile).