Associated with a prodigious event which occurred in 206 B.C., the altar of Neptune at the Circus Flaminius must have been built during the last decades of the 3rd century B.C. It was later substituted by the temple dedicated by Cn. Domitius Ahenobarbus around 125 B.C. mentioned in sources of Imperial date. The latter complex, whose position is confirmed in the inscription CIL VI, 8423, is represented on an aureus of 41 B.C. (RRC 519), which shows a tetrastyle building on a podium. One of the statues from the temple (Ares Ludovisi = Achilles), seen and mentioned by Pliny, was found in 1621 at piazza Costaguti. In the same area recent excavations have uncovered the remains of the temple, below the 15th century house of L. Manlio between via del Portico di Ottavia and piazza Costaguti.