Discovered in 1940 within the sacellum devoted to Attis, in the campus of the Magna Mater at Ostia, this circular altar-made of mainland Greece marble- was assembled from separately worked blocks.
Between an upper frame, with ovules and lancets, and a lower frame with heart-shaped leaves, the Twelve Gods (some are missing from the upper section) are represented in a sculpted sequence beginning with the “central” figure of Zeus enthroned, derived from an original statue sculpted by Phidias. Above him, near the edge of the altar, is the Greek inscription ΔΩΔΕΚΑ ΘΕΩΝ. From left to right follow Hera, Demeter, Poseidon, Aphrodite, Ares, Hephaestus, Hermes, Hestia, Apollo, Artemis and Athena, all modelled on great Fourth Century BCE originals (so much so that it has been argued they could be copies of the dodekatheon, the series of the Twelve Olympians described by Pausanias and sculpted by Praxiteles for the Temple of Artemis Soteira in Megara, Greece). This indicates that the altar can be considered the work of a Greek-trained workshop active in the second half of the First Century BCE or, to be more precise, during the Augustan era.