The site was excavated by W. F. Grimes, director of the Museum of London, and Audrey Williams in 1954.
The temple, initially hoped to have been an early Christian church, was built in the mid-3rd century and dedicated to Mithras or perhaps jointly to several deities popular among Roman soldiers.
Then it was rededicated, probably to Bacchus, in the early fourth century.
Found within the temple, where they had been carefully buried at the time of its rededication, were finely detailed third-century white marble likenesses of Minerva, Mercury the guide of the souls of the dead, and the syncretic gods Mithras and Serapis, imported from Italy.
There were several coarser locally-made clay figurines of Venus, combing her hair.
The artefacts recovered were put on display in the Museum of London.

Among the sculptures the archaeologists found was a head of Mithras himself, recognizable by his Phrygian cap.
The base of the head is tapered to fit a torso, which  was not preserved.

Artefacts found in Walbrook in 1889 probably came from the Mithraeum, according to the archaeologist Ralph Merrifield, although this was not identified at the time (Merrifield 1965, p. 179).
One was a marble relief, 0.53 m tall, of Mithras in the act of killing the astral bull, the Tauroctony that was as central to Mithraism as the Crucifixion is to Christianity.
On it Mithras is accompanied by the two small figures of the torch-bearing celestial twins of Light and Darkness, Cautes and Cautopates, within the cosmic annual wheel of the zodiac.
At the top left, outside the wheel, Sol–Helios ascends the heavens in his biga; at top right Luna descends in her chariot.
The heads of two wind-gods, Boreas and Zephyros, are in the bottom corners.
It bears the inscription
VLPIVS SILVANVS EMERITVS LEG II AVG VOTVM SOLVIT FACTVS ARAVSIONE
which may be translated "Ulpius Silvanus, veteran soldier of the Second Augustan Legion, in fulfilment of a vow, makes this altar [as the result of] a vision" or "Ulpius Silvanus, veteran of the Second Legion Augusta, fulfilled his vow having become (a Mithraist) at Orange" [University of Edinburgh, Classics Department, teaching collection] (Collingwood and Wright 1965, No.
3).

Nearby were buried heads of the Roman goddess Minerva and a finely detailed bearded head of Serapis, Jupiter-like in his features but securely recognizable by the grain-basket, the modius, upon his head, a token of resurrection.

An inscription dateable AD 307–310 at the site
PRO SALVTE D N CCCC ET NOB CAES DEO MITHRAE ET SOLI INVICTO AB ORIENTE AD OCCIDENTEM
may be translated "For the Salvation of our lords the four emperors and the noble Caesar, and to the god Mithras, the Invincible Sun from the east to the west" (Collingwood and Wright 1965, no.
4).

Parallel to the construction work between 2010 and 2014, Museum of London Archaeology led a team of over 50 archaeologists in further excavations of the site.
Excavation recovered more than 14,000 items, including a large assembly of tools.
The varied objects are thought to have been brought to the site in landfills and soils collected elsewhere and laid down to improve the marshy banks of the River Walbrook during the rebuilding of London after the Boudican revolt of AD 60 or 61.

The local waterlogged soil conditions then preserved even organic material like leather shoes and a large assembly of wooden writing tablets of which over 400 were found.
The tablets originally held a layer of dark wax and messages were scratched into the wax with a stylus that revealed the paler wood underneath.
The wax has perished, but the words were reconstructed from scratch marks left in the wood.
Among the messages is the oldest financial document from London, dated AD 57, and two addresses from AD 62 and AD 70 containing the earliest mention of London.
The site was excavated by W. F. Grimes, director of the Museum of London, and Audrey Williams in 1954. The temple, initially hoped to have been an early Christian church, was built in the mid-3rd century and dedicated to Mithras or perhaps jointly to several deities popular among Roman soldiers. Then it was rededicated, probably to Bacchus, in the early fourth century. Found within the temple, where they had been carefully buried at the time of its rededication, were finely detailed third-century white marble likenesses of Minerva, Mercury the guide of the souls of the dead, and the syncretic gods Mithras and Serapis, imported from Italy. There were several coarser locally-made clay figurines of Venus, combing her hair. The artefacts recovered were put on display in the Museum of London.
Among the sculptures the archaeologists found was a head of Mithras himself, recognizable by his Phrygian cap. The base of the head is tapered to fit a torso, which  was not preserved.
Artefacts found in Walbrook in 1889 probably came from the Mithraeum, according to the archaeologist Ralph Merrifield, although this was not identified at the time (Merrifield 1965, p. 179). One was a marble relief, 0.53 m tall, of Mithras in the act of killing the astral bull, the Tauroctony that was as central to Mithraism as the Crucifixion is to Christianity. On it Mithras is accompanied by the two small figures of the torch-bearing celestial twins of Light and Darkness, Cautes and Cautopates, within the cosmic annual wheel of the zodiac. At the top left, outside the wheel, Sol–Helios ascends the heavens in his biga; at top right Luna descends in her chariot. The heads of two wind-gods, Boreas and Zephyros, are in the bottom corners. It bears the inscription
VLPIVS SILVANVS EMERITVS LEG II AVG VOTVM SOLVIT FACTVS ARAVSIONE
which may be translated "Ulpius Silvanus, veteran soldier of the Second Augustan Legion, in fulfilment of a vow, makes this altar [as the result of] a vision" or "Ulpius Silvanus, veteran of the Second Legion Augusta, fulfilled his vow having become (a Mithraist) at Orange" [University of Edinburgh, Classics Department, teaching collection] (Collingwood and Wright 1965, No. 3).
Nearby were buried heads of the Roman goddess Minerva and a finely detailed bearded head of Serapis, Jupiter-like in his features but securely recognizable by the grain-basket, the modius, upon his head, a token of resurrection.
An inscription dateable AD 307–310 at the site
PRO SALVTE D N CCCC ET NOB CAES DEO MITHRAE ET SOLI INVICTO AB ORIENTE AD OCCIDENTEM
may be translated "For the Salvation of our lords the four emperors and the noble Caesar, and to the god Mithras, the Invincible Sun from the east to the west" (Collingwood and Wright 1965, no. 4).
Parallel to the construction work between 2010 and 2014, Museum of London Archaeology led a team of over 50 archaeologists in further excavations of the site. Excavation recovered more than 14,000 items, including a large assembly of tools. The varied objects are thought to have been brought to the site in landfills and soils collected elsewhere and laid down to improve the marshy banks of the River Walbrook during the rebuilding of London after the Boudican revolt of AD 60 or 61.
The local waterlogged soil conditions then preserved even organic material like leather shoes and a large assembly of wooden writing tablets of which over 400 were found. The tablets originally held a layer of dark wax and messages were scratched into the wax with a stylus that revealed the paler wood underneath. The wax has perished, but the words were reconstructed from scratch marks left in the wood. Among the messages is the oldest financial document from London, dated AD 57, and two addresses from AD 62 and AD 70 containing the earliest mention of London.
London Mithraeum