From: M. I. Rostovtzeff &c, The excavations at Dura-Europos. Preliminary report of the seventh and eighth seasons of work, Yale, 1939. Plate III, 2: "Middle Mithraeum altars (p.75) and Late Mithraeum sanctuary."
The cult niche.
The main altar (see fig. 12, 1).
ILN 1934, fig. 4; Report, 66, 75 and fig. 31; Pl. III, 2.
"All of plaster, the main altar had a square base topped by a quarter-round
molding from which sprang the columnar engaged shaft. The top, 0.73 square
with a molded point at each corner, projected for one third of its width over the
altar table. The central depression was blackened and contained cinders.
To the left of this large altar, 0.08 lower than the altar table and attached to it,
were two smaller altars of molded form. Their bases and tops were square, changing
in an unbroken surface to a rounded central shaft. The corners of each top were
brought to a point.
The central depression of 3 was rimmed with a ring of plaster
opened in front to form a nearly closed horse-shoe and the rim had aronnd its
edge twelve equally spaced holes about 0.004 in diam. The central depression
of 2 was rimmed with a simple smooth ring of plaster.
Both altars contained marks of fire and cinders, although their material and position would not have allowed a
hot or continuous fire to burn there".