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 colossal ruined temple in the center of the Greek capital Athens that was dedicated to Zeus, king 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.