San Clemente: three buildings stacked, and the oldest Italian on a wall

The church did not sink. Rome rose.

This is the thing to understand before anything else. San Clemente is not a building that subsided. Rome's ground level rose around it — rubble, flood silt, collapse and rebuilding raised the city's floor century after century, and each generation built on the last because the old walls made excellent foundations.

That is why Rome is not a city with ruins in it. It is a stack, and this is the clearest place to walk through a section of it.

The church at street level, c. 1099–1120

The basilica you enter was built in a single campaign under Cardinal Anastasius, about 45 metres by 25, with three naves on arcades of ancient marble and granite columns.

Those columns were second-hand when the church was new — spolia, reused ancient material, which is not laziness but an attitude to a city with a great deal of it lying around. The floor is Cosmatesque inlay, roundels of porphyry and green serpentine in geometric frames.

The marble schola cantorum standing free in the nave is older than the building around it. Its panels were lifted out of the earlier basilica below and reinstalled up here; some carry the monogram of a pope of the 530s. Somebody around 1100 knew exactly what he was burying, and saved a piece of it.

The apse: a Cross that grows

The half-dome carries the Triumph of the Cross, dated variously to the twelfth century or to around 1200. From the foot of the Crucifixion an acanthus vine spirals outward and fills the entire vault in gold-ground scrolls, with twelve doves on the Cross itself.

Worked into those scrolls are birds, deer, shepherds, doctors of the Church — and, by most accounts, a woman feeding chickens and a man with a fishing rod. The argument in coloured glass is that the Cross is not the end of anything. It is the root, and everything grows out of it.

Off the left aisle, the Chapel of Saint Catherine was frescoed by Masolino da Panicale in the 1420s: early Renaissance painting with real perspective, inside a Romanesque church. Almost everybody walks past it on the way to the stairs.

One level down: a church sealed for seven centuries

The fourth-century basilica is securely attested by 392, when Jerome refers to a church in Rome dedicated to Clement. Councils were held in it in 417 and 499.

Because the church above stands on it, you walk through corridors between foundations rather than an open room. The walls carry the largest collection of early medieval wall painting in Rome after Santa Maria Antiqua — and they survive precisely because the church was filled with earth and rubble around 1100 and forgotten. Burial preserved them. Being open again is far harder on them than the dark was.

The oldest Italian anybody has found, and it is obscene

One fresco down here shows a Roman official called Sisinnius ordering his servants to drag Saint Clement away in chains. They are not dragging Clement. They are dragging a column, because they have been struck blind to the saint and have not noticed.

Beside them, their speech is painted in — and it is not Latin. It is the street language of eleventh-century Rome: early vernacular Italian, and it is among the earliest written Italian known. The servants are swearing at each other, coarsely, and telling one another to pull harder. Clement replies in Latin, very grandly, that they deserve to drag stones for the hardness of their hearts.

Two languages in one picture — the old holy one, and the new one everybody actually spoke. It survives because a lay couple, Beno de Rapiza and Maria Macellaria, paid for the cycle and wanted the joke to land with ordinary Romans. They had themselves painted into it.

Also down here is the tomb of Saint Cyril, who with his brother Methodius devised the alphabet that made written Slavonic possible. He died in Rome in 869, and Slavic pilgrims still come for him specifically.

Two levels down: first-century Rome, and a temple of Mithras

At the bottom, roughly six or seven metres below the modern street, are an alley, an insula — a Roman apartment block — and a heavy tufa building that may have been the imperial mint. That identification is argued from scale and position, not from an inscription.

In the courtyard of the insula, around 200 AD, worshippers installed a Mithraeum. Its main chamber is about 9.6 by 6 metres, with benches down both long sides for the ritual meal and a vaulted ceiling made to resemble a cave. The altar at the end is carved with the tauroctony — Mithras in a Phrygian cap killing the bull — with the torchbearers Cautes and Cautopates on its sides.

Mithraism was a men-only cult with seven grades of initiation, running from Syria to the north of Britain. It was banned in 395 along with the other pagan religions and simply vanished.

We know in detail what its initiates did. We have almost no idea what they believed: the cult left identical images across the empire and not one word of explanation written by anyone who believed it.

And the whole way down, you can hear water. There is a stream moving through Roman drains at the lowest level, and it has never stopped.

An Irish friar found all of it

The Irish Dominicans have held San Clemente since the seventeenth century, given it as a refuge when Catholic clergy could not train in Ireland. In 1857 their prior, Father Joseph Mullooly from County Longford, worked out that the proportions of his own church implied something buried beneath it, and dug.

He found the fourth-century basilica, then the Roman city. The Mithraeum was found in 1867 — and then could not properly be investigated for nearly fifty years, because it was flooded. A drainage tunnel driven in the years around 1912–1914 carried the water off to the old Roman sewer. Visitors reach the lowest level today because of Edwardian hydraulic engineering.

Mullooly is buried in the church he dug through.

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How long you need

Long enough to go down twice and come back up. The basilica above is free to enter and takes ten minutes; the excavations are ticketed and are the reason to come. The lower levels are dark, cool and almost entirely uninterpreted, which is exactly the situation a long audio guide is for.