The Mithraeum was discovered in February 1934 on the N.W. side inside the rempart of Dura-Europos (Es-Sâlihiyeh) between gate 24 and 23. After the excavations it was transported to New Haven, Gallery of Fine Arts of Yale University.«When the Mithraeum was founded in about 168 A.D. it consisted of three apartments. Room A (L. 4.65 Br. 5.80), the Mithras shrine, was entered by an axial door through a partition separating it from a central chamber B (L. 5.75 Br. 3.50), originally a house diwan, that opened into a courtyard D tot the south, and a small chamber C (L. 3.50 Br. 3.50) to the east».A was divided into three parts: a paved passage with on either side the benches b and c (H. 0.72 Br. 1.70), in which the columns 1 and 2 had been built to support the ceiling, which was approximately 1.65 high over their benches, but about 1.60 higher over the central aisle.Via the stairs d a rectangular, raised platform a (H.0.88), in which a round well 9 (diam. 0.32). In front of a stood the main altar with two smaller side-altars, whereas against the backwall two reliefs had been fixed.About 210 A.D. a first rebuilding took place, because in the general destruction of the quarter the early Mithraeum was also destroyed. The entire sanctuary was enlarged considerably. «The new alterations consisted of adding an antechamber B to the Mithras shrine by taking out the dividing partition and adding two more colums 3 and 4 on the foundations of the wall (L. 10.90); of building a small room E (l. 5.60 Br. 1.65) on the south and a low bench on the north of this new addition (H. 0.40 Br. 1.70); of turning the east chamber C into a vestibule and porch; of constructing an arched niche back of the altar; and of redecorating the entire chmaber».Opposite a rectangular recess (L. 1.25 Br. 0.75) in the new podium, there was a basin 10 in the middle of the paved floor (diam. 0.32), another basin 11 was situated in the former room C. underneath the columns 3 and 4 two altars e and f were placed.Finally in ca 240 A.D. a second reconstruction took place, which resulted in the definitive shape of the sanctuary. «It is probable that the roof was removed and altered for the construction of the new vaulted spelaeum and the additional columns (5, 6, 7, 8). In the Late Mithraeum, the chamber fo the south E was entirely removed and in its place was built a bench, probably low; the low bench on the north side was heightened to the level of the upper benches; two more columns were added to either side, making the chamber more symmetrical; two chambers F (L. 3.25 Br. 6.00) and G (L. 2.50 Br. 6.00) to the north of the building, the earlier history of which is obscure, were joined to the Mithraeum, a narrow passageway being cut through the benches leading to a newly pierced doorway. For the new altar table the aisle between the benches was filled up to the bench level as far as the first pair (1, 2) of columns and a stair of seven steps was built against the face of this platform. Between the first pair of columns and the wall were built partitions that supported a vault covering the new raised platform.When the walls behind the Mithraeum had to be strengthened against the impendency of the Persians under Sapor, the sanctuary got buried under the sand at the capture of the fortification in 256 A.D.