It is dated to the later 2nd century BC and was built either by
L. Mummius Achaicus, conqueror of the
Achaeans and destroyer of
Corinth, or by the
trader Marcus Octavius Herrenus in gratitude for success in business. The temple is 14.8 m in diameter and consists of a circular
cella within a concentric ring of twenty
Corinthian columns 10.66 m tall, resting on a
tuff foundation. These elements supported an
architrave and roof, which have disappeared. The original wall of the cella, built of
travertine and marble blocks, and nineteen of the originally twenty columns remain but the current tile roof was added later.
Palladio's published reconstruction suggested a dome, though this was apparently erroneous. The temple's original dedication is dated back to circa 143-132 BC, a time when intense construction was taking place in Portus Tiberinus. ==Identification==