The Mithraeum of San Clemente in Rome: an underground temple devoted to Mithras

Last Updated on 2022/10/10

The Mithraeum of San Clemente in Rome

The Mithraeum is a building from the Roman imperial period buried several meters below the Basilica of San Clemente del Laterano in Rome, located between the Esquiline and Caelian hills, in the extension of the Colosseum and the Ludus Magnus. Discovered in 1867 and excavated in the early 20th century, it is accessible to tourists from the Basilica of San Clemente.

The god Mithras was the center of adoration in the ancient Hellenistic religion of Mithraism.

The Temple of Mithras was discovered in 1869 during excavations in the underground basilica of San Clemente. The events of 1870 (annexation of the Papal States by King Victor Emmanuel II) interrupted the excavations, while the site was gradually flooded. The recurrent flooding of the area forced the construction of a drainage channel between June 1912 and May 1914, with the digging of a 600-meter long tunnel 14 meters below ground level, through layers cluttered with archaeological remains, to reach an ancient sewer near the Colosseum. 

Various Roman structures are found beneath the lower basilica of San Clemente. A building with a rectangular base and walls made of large blocks of tufa from the Aniene is the oldest building. The short side measured 29.60 meters, while the long side is not completely unearthed. 

Some rooms covered by a barrel vault made with reticulated work (opus reticulatum, a form of brickwork used in ancient Roman architecture) line the outer wall. Based on the building technique, this structure can be dated to the beginning of the 1st century BC, before the great fire of 64. 

The dating and interpretation of the use of this building is disputed. 

According to Filippo Coarelli, these rooms could be a mint, built after the fire of the Capitoline mint in the year 80.

The Mithraeum

A second building rests on the eastern wall of the building below the basilica. This dwelling, built entirely of brick, dates from the time of Domitian, around 90-96 according to the stamps on the bricks, and covered an older building damaged by the fire of 64. In what was the ground floor, there were four large rooms, two of which had a stuccoed vault; and a corridor surrounding an inner courtyard; a staircase on the south side led to the upper level of which only the eastern wall and some partitions remain, up to ten meters high. The central courtyard was covered by a low barrel vault, with skylights to provide light. Later, the access to this courtyard was modified by closing the entrance door and opening four other side doors.

During the time of the Severans (193-235), the courtyard of this house was transformed into a Mithraeum: the exits facing each other were closed and the ceiling of the barrel vault was decorated with stars, according to the symbolism of Mithraic cosmology. At the back of the courtyard, the statue of the god Mithras was placed in a niche and the altar, still in place, with Mithras sacrificing the bull on the front and the torchbearers Cautes and Cautopates on the sides. An inscription indicates the name of the altar’s donor: Cn(aeus) Arrius Claudianus pater posuit. Along the walls are aligned masonry benches for the faithful.

The Mithraeum bears several traces of destruction, before its definitive abandonment towards the end of the fourth century, probably linked to the transformation of the place into a Christian basilica.

Mithraists called themselves syndexioi, those “united by the handshake”. They met in underground temples, now called mithraea, like the Mithraeum of San Clemente. The cult had its center in Rome and was popular throughout the empire. In the 4th century, worshipers of Mithras faced persecution from Christians and the religion was subsequently suppressed by the end of the century.

Other notable Mithraea in Rome

Featured image: Mithraeum under the basilica of Saint Clement in Rome (author: Allie Caulfield)
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