Originally an Iranian god, Mithras became especially popular in the Roman period among soldiers and the merchant class. It is not surprising, therefore, to find that he had a special status in the military garrison at Dura-Europos.
In 1933–34, during the seventh season of the excavations at Dura-Europos by Yale University and the French Academy of Inscriptions and Letters, a small shrine to Mithras was discovered along the western fortification wall in the northern part of the city. A dedicatory inscription found there, dated about A.D. 168–69, shows that the shrine was sponsored by Palmyrene archers who served in the Roman army.
There is no evidence of any earlier Mithraeum; it seems safe to assume that the god Mithras was not worshipped in Parthian Dura-Europos but came to the city with the Romans. The Mithraeum was rebuilt and augmented after the enlargement of the garrison in A.D. 209–11. An inscription from this phase shows that the dedicant of the renovation was a centurion named Antonius Valentius.

The building underwent yet another reconstruction and enlargement around A.D. 240. The decorations from this final phase were preserved by a defensive dirt embankment when the city was conquered by the Sasanians around A.D. 256 and are now part of the Yale University Art Gallery’s Dura-Europos Collection.
The cult of Mithras was a mystery religion that featured initiation, banquets, and the promise of salvation after death. Only men were allowed to join. Due to the exclusive nature of the cult, little is known about its rituals. There were seven levels, or grades, of initiation; graffiti at Dura-Europos listed names of initiates, given along with their Mithraic grade. Shrines dedicated to Mithras were generally located underground, commemorating the god’s birth in a cave; the Dura-Europos Mithraeum was unusual in that it was totally above ground.
The devotional focus of a Mithraic shrine was typically a cult relief showing Mithras slaying the Cosmic Bull (in a depiction known as the tauroctony), which symbolized the victory of light over primeval darkness.

While iconographic schemes varied among Mithraic shrines in different locations, this image was a constant. The Dura-Europos Mithraeum contained two such reliefs (at right). Their inscriptions show that they date from the earliest phase of the shrine. The only surviving elements of that phase, the reliefs were reused as cult images in each subsequent renovation. Both show Mithras and the Bull in characteristic fashion: Mithras, dressed in Persian costume, sits on the back of the Bull and pulls his head back with one hand while he stabs the animal in the neck with the other. A small dog drinks blood from the wound. In the larger of the two reliefs, the donors or dedicants of the relief are shown observing the scene. Mithraic iconography from this period generally omits donor images, so their presence here is another deviation for which the Dura-Europos shrine is notable.
A series of paintings showing scenes from the life of Mithras (including the slaying of the Bull, this time in a landscape with trees and altars), as well as representations of the signs of the zodiac, surrounded the reliefs.

The reliefs were flanked on both left and right by single seated figures who, like Mithras, wear Eastern dress. Russian scholar and Yale professor in the 1920s Michael I. Rostovtzeff proposed that the two were members of the shrine’s Palmyrene congregation, although others have suggested that they are prophets or magi.
On the side walls of the niche were two virtually identical scenes of Mithras as a mounted archer hunting wild animals in a wood. These hunting scenes are particularly Iranian in character and display an Eastern sensibility unlike other depictions of Mithras in the western Roman Empire. They emphasize the god’s role as divine archer, one that would have carried special meaning for the Palmyrene archers who worshipped him at Dura-Europos.