The Temple of Olympian Zeus (Greek: Ναός του Ολυμπίου Διός, Naos tou Olympiou Dios), also known as the Olympieion or Columns of the Olympian Zeus, is a monument of Greece and a former colossal temple at the centre of the Greek capital Athens. It was dedicated to Olympian Zeus, a name originating from his position as head of the Olympian gods. Construction began in the 6th century BC during the rule of the Athenian tyrants, who envisaged building the greatest temple in the ancient world, but it was not completed until the reign of the Roman Emperor Hadrian in the 2nd century AD, some 638 years after the project had begun. During the Roman period the temple -that included 104 colossal columns- was renowned as the largest temple in Greece and housed one of the largest cult statues in the ancient world.
The temple's glory was short-lived, as it fell into disuse after being pillaged during a barbarian invasion in the 3rd century AD, just about a century after its completion. It was probably never repaired and was reduced to ruins thereafter. In the centuries after the fall of the Roman Empire, it was extensively quarried for building materials to supply building projects elsewhere in the city. Despite this, a substantial part of the temple remains today, notably sixteen of the original gigantic columns, and it continues to be part of a very important archaeological site of Greece.
The temple is located approximately 500 m (1640 feet) south-east of the Acropolis, and about 700 m (2,300 feet) south of the center of Athens, Syntagma Square. Its foundations were laid on the site of an ancient outdoor sanctuary dedicated to Zeus. An earlier temple had stood there, constructed by the tyrant Peisistratus around 550 BC. The building was demolished after the death of Peisistratos and the construction of a colossal new Temple of Olympian Zeus was begun around 520 BC by his sons, Hippias and Hipparchos. They sought to surpass two famous contemporary temples, the Heraion of Samos and the Temple of Artemis at Ephesus, which was one of the Seven Wonders of the Ancient World. Designed by the architects Antistates, Callaeschrus, Antimachides and Pornius, the Temple of Olympian Zeus was intended to be built of local limestone in the Doric style on a colossal platform measuring 41 m (134.5 feet) by 108 m (353.5 feet). It was to be flanked by a double colonnade of eight columns across the front and back and twenty-one on the flanks, surrounding the cella.