a monumental altar erected in the northern Campus Martius near the via Lata, one of the major products of Augustan public art. It was voted in 13 bc by the senate, as Augustus records in his Res Gestae, to commemorate his safe return from Gaul and Spain; and finished in 9. The altar proper was surrounded by a walled precinct with entrances to east and west, and decorated with sculptured reliefs on two tiers. Internally there were festoons slung from ox‐heads above and fluting below; externally the lower frieze was filled with complex acanthus scrolls, above which on the east and west were mythical panels, on the north and south a religious procession showing the imperial family, lictors, priests, magistrates, and representations of the Roman people. Smaller reliefs on the inner altar, showing Vestals, priests, sacrificial animals, etc., continue the procession on the outer walls. The event represented by this procession is disputed.
In 1937–8 the site was thoroughly explored and the monument reconstructed, with most of its surviving sculptures, between the Mausoleum of Augustus and the Tiber. See sculpture, roman.