Located in southern Athens, between the Acropolis and the Ilissos river, the Olympeion or Temple of Olympian Zeus was the sanctuary of Olympian Zeus. Here stands one of the greatest ancient temples of Zeus and, according to Vitruvius, one of the most famous marble buildings ever constructed. The sanctuary’s foundation is attributed to mythical Deukalion. The site also comprises the temple of Apollo Delphinios – the sanctuary of Apollo Delphinios was traditionally associated with Theseus – and a tripartite building with a south courtyard of ca. 500 BC. The latter has been identified as the Delphinion Court, which was allegedly founded by Aegeas.
The site of the Olympeion was a place of worship of chthonic deities and of ancient Athenian heroes Athens since prehistory. Peisistratus the Young initiated the construction of a monumental temple in 515 BC, but failed to complete his project because of the fall of tyranny. The temple remained unfinished for approximately 400 years, until Antiochus IV Epiphanes resumed its construction in 174 BC. It was completed in AD 124/125 by Emperor Hadrian, who associated himself with Zeus and adopted the title of Olympios. A large poros temple dedicated to Apollo Delphinios was also built on the site around 450 BC. It was abandoned in the third century AD. The temple was Doric peripteral with two columns in antis on the front and back. In the second century AD, Hadrian built a Roman temple of the Doric order, with a built enclosure and an outdoor altar, probably of Kronos or Rea.

A new city wall, the so-called Valerian Wall, was erected under Emperor Valerius in the third century AD, possibly on the same line as the Classical Themistoclean Wall. A large Late Roman cemetery developed outside the wall in the fourth and fifth centuries AD, and an extensive Byzantine settlement with many houses and workshops, including tanneries and an olive press, developed over the ruins of the Classical temple in the eleventh-twelfth centuries. This settlement had at least one main street, the so-called Ancient Street.