The Mithraeum of the House of Diana was excavated in the years 1914-1915. It was installed in two Antonine rooms in the north-east corner of the House of Diana at the end of the second or in the early third century AD.
In the south-west corner of the southern room were two doors. The door in the west wall was blocked when the mithraeum was installed. In the blocking is a semicircular niche. Between the southern and northern room are two doors (the central one was originally a window). The northern room received indirect light, and was quite dark. Podia (h. 0.60) were built in both rooms. Those in the southern room have disappeared, but an older geometrical black-and-white mosaic testifies to their existence. Between the southern podia is a well, belonging to the mithraeum. Below the podia in the northern room was also a black-and-white geometrical mosaic. These podia were reached along a few treads at the south end.
Plan of the mithraeum. SO II, fig. 1.
Against the back wall of the northern room are an altar (h. 0.78) and an aedicula (h. 3.20). The aedicula is covered with white plaster, with some red accents. To the left and right of the niche of the aedicula were stucco semi-columns, resting on travertine consoles. The vault of the niche was decorated with pieces of pumice and blue paint, referring to the mithraic cave. The altar had been taken to the mithraeum from elsewhere (see the Tempio d'Ercole (I,XV,5)), and a round hole, perhaps for a lamp behind glass, was hacked out from one side to the other. In the mithraeum it was put up bottom-up. Part of the top, that had now become bottom, was missing, and replaced by masonry. The missing fragment was found by the excavators on the Cardo Maximus. The altar was put up by M. Lollianus Callinicus, witness the following inscription, that was added:
ARAM DEO DO(no) DE(dit)
The same "father" (main priest) is known from an inscription found in a shop on the Decumanus, near the House of Diana, put up by Petronius Felix Marsus. The inscription may well have belonged to the mithraeum in the House of Diana:
[M. Lollia]NO CALLINICO
[patre pet]RONIVS FELIX
[Marsus sign]VM DEO
[do(no)] DE(dit) D(edicavit)
[---] ATVS XINV
This inscription was reused by two Marci Caerellii, Hieronimus and [---]us, priests of Mithras. On the back is the inscription:
M.M. CAER[ellii Hiero]
NIMVS ET [---]
VS SACERDO[tes et antisti]
A Cerell(ius) Ieronim(us), probably our Hieronimus, is mentioned in an inscription from 198 AD, as a member of the fabri tignuarii. At some point in time a stable with trough was installed in the House of Diana, probably for animals that operated millstones in a nearby bakery, such as the adjacent Caseggiato dei Molini (I,III,1). It is probably significant that other Marci Caerellii (Iazemis and Zmaragdus) were leading figures in the guilds of the bakers in Ostia and Rome.
Returning to the older inscription, we may note that Callinicus and Marsus are documented in yet another inscription, found in Via della Fontana in 1899:
M. LOLLIANO CALLINICO PATRE
PETRONIVS FELIX MARSVS
SIGNVM ARIMANIVM DO(no) DE(dit) D(edicavit)
The inscription is on an architrave that belonged to an aedicula, but we can only speculate about the original location. It does not seem to belong to this mithraeum. The inscription mentions a depiction of the Persian deity Arimanius, who played a role in the cult of Mithras as manifestation of Hades. The name Marsus suggests, that this individual was a snake-charmer, who was thought to have occult powers.
In the left part of the base of the aedicula is a marble head of Dionysus. Above the head is a graffito:
To the left may be names of slaves. To the right the word BINV is probably vinum, wine, appropriate above the head of Dionysus. The right column probably mentions votive offerings.
The altar and aedicula in the northern room. Photograph: Eric Taylor.
The marble head of Dionysus in the base of the aedicula.
Photograph: Eric Taylor.