View of the Temple of Olympian Zeus as seen from the Acropolis. Photograph source: http://travelpassionate.com/mythological-tour-of-athens/
This date marks the Olympeia, an Athenian festival honoring Olympian Zeus. It was associated with the temple overlooking the Ilissos River conceived by the tyrant Pisistratus in the 6th century BCE. Building on such a monumental scale in that era was scorned as an act of hubris.
This view of the Temple of Olympian Zeus in Athens gives an idea of the enormous size of the building in question. Construction was abandoned in 510 after the tyrants had been expelled and a democracy established in Athens.A Roman architect was hired in 174 BCE by Antiochus IV Epiphanes to complete the temple, but it remained unfinished when the king died a decade later. It was finally completed by the Emperor Hadrian, and dedicated in 132 CE. The temple of Olympian Zeus was renowned in the Roman era as the largest temple in Greece.