In the heart of modern Athens, its streets pulsating with traffic, stands an enormous open space bordered by trees and shrubs – the Olympieion – a tranquil archaeological park where earth and sky seem to meet, linked by massive marble columns stretching upward, marking the temple of Olympian Zeus. Once inside the entrance of this age-old sanctuary, visitors are treated to a taste of nature, an extraordinary ancient ruin on a super-human scale and one of the area’s most inspiring views of the temple-topped Acropolis.
Like the Acropolis, the temple of Olympian Zeus has been a distinctive Athenian landmark since time immemorial. Begun about 520 BC by the tyrant Peisistratus and his sons, it was left unfinished at the end of their rule until the 2nd century BC, when further construction was briefly undertaken (174 – 164 BC) by one of Athens’ Hellenistic benefactors, the Seleucid king Antiochus IV Epiphanes. Abandoned once again following Antiochus’ death, it was ultimately finished by the Roman emperor Hadrian and dedicated in AD 132. Hadrian, an ardent Hellenophile much respected by the people of the Greek East, gave Athens not only the completed Olympieion, but also other temples in the area; a new public forum on the north side of the Acropolis that contained a library and lecture halls; and an urban water system fed by an aqueduct from Mount Penteli that continued to supply the city until the 1930s.
https://whyathens.com/temple-of-olympian-zeus/