Temple of Hercules Victor

Rome's oldest surviving marble building (late 2nd century BC) — a small round temple in the Forum Boarium beside the Tiber, built using imported Greek marble in the elegant Greek peripteral style. Often misidentified as a temple to Vesta because of its round shape (and confusingly nicknamed 'Temple of Vesta' in older sources). It survived because it was converted into the church of Santa Maria del Sole in the Middle Ages. Free to view from the outside; interior visits are rare.