The Mithraeum of the Seven Gates (7.05 x 5.80) was built in a cella in the south-east corner of horrea from the first century AD (IV,V,12). In the back wall a square, arched wall-niche was made. Brick podia were set against the lateral walls, and a floor mosaic and paintings were added. The installation took place in the years c. 160-170 AD (see the Mitreo delle Sette Sfere (II,VIII,6) for Beck's interpretation).
The shrine is entered through a door two metres wide, with a travertine threshold with pivot holes for two doors opening inwards. The podia were reached along a few brick treads. In the vertical side of the podia, halfway down the shrine, are rectangular niches. In both a small, rectangular, marble altar was found. In the southern niche a terracotta vessel had been buried, in which bones were found of poultry and perhaps rabbits, plus three small, broken, ovoid vessels.
At a distance of 1.80 from the back wall is a round terracotta vessel in the floor, 0.25 deep. On either side is a small, square, marble slab. They are both pierced by a lead water-pipe. At 0.40 from the back wall is a square masonry altar (0.45 x 0.50, top missing), decorated with white plaster. A semicircular or round, horizontal hole passed through the entire altar. It was closed off by glass, of which fragments were found. Behind the glass was probably a lamp. The altar rests on a marble column base, below which a second-century coin was found of Faustina Minor, with a depiction of Ceres. Nearby a terracotta lamp for six wicks was found.
Behind the altar is a large, arched wall-niche (starting at h. 1.40, w. 1.50, h. 0.80, d. 0.30). It was painted blue with red spots. The central part of the back wall of the shrine was painted red, the colour of the sun and fire. Above the podia, both on the east and north wall, and on the west wall is a garden painting, with among others palm trees. The garden is a symbol of rebirth. On the west part of the south wall are two panels, separated by a red band. On the lower panel a red and yellow geometric object can be seen, on the upper panel a disc.
Between the podia is a black-and-white mosaic. Behind the threshold is a central gate flanked by columns supporting an arch with battlements or pinnacles. An oscillum is hanging down from the arch. On either side are three minor gates, separated by columns, with battlements. The seven gates are a reference to the seven planetary spheres through which the souls of the initiates passed. The seventh gate is made of gold and belongs to Sol.
There are also mosaic depictions on the vertical side of the podia. On small pilasters near the door, badly preserved, must have been mosaic depictions of Cautes and Cautopates, the former with a cock and a raised torch, the latter with a lowered torch, symbols of, respectively, the morning and evening. Four planets are depicted on the podia. On the front part of the right podium is Mars with a helmet, a lance in his right hand, and a trophee with cuirass resting on his left shoulder. Further on is Luna, a naked woman with a moon crescent on her head. On the front part of the left podium is Venus Anadiomene. In the centre is a naked Mercurius, with purse and caduceus. Also on the vertical side and on the horizontal rim of the podia are floral motifs.
Two more planets are depicted on the floor. In the back part is a standing, bearded Jupiter, with a bolt of lightning and a sceptre. Near the back wall a bearded bust with a pruning knife represents Saturnus. The seventh planet, Sol, was represented by Mithras who must have been depicted in the niche.
In front of Jupiter we see a krater, symbol of the water in the cave of Mithras, a snake emerging from a rock, symbol of the earth, and a bird, probably an eagle, symbol of the air. The object in front of the eagle is probably a bolt of lightning, symbol of the fire.
The following objects were found:
Plan of the mithraeum. North is to the left.
SO II, fig. 20.