Basilica of Neptune
Rome, Italy
The Basilica of Neptune (Basilica Neptuni) was an ancient Roman basilica constructed c. 25 BCE under Marcus Vipsanius Agrippa in honour of Neptune to celebrate his naval victories at Mylae, Naulochus and Actium. Surviving fragments of the basilica remain visible on the Campus Martius in Rome.
Archaeological site data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).