Delphi was the site of the Delphic oracle, the most important oracle in the classical Greek world, when it was a major site for the worship of the god Apollo after he slew the Python, a deity who lived there and protected the navel of the Earth. His sacred precinct in Delphi was a panhellenic sanctuary, where every four years athletes from all over the Greek world competed in the Pythian Games, one of the four panhellenic games, precursors to the Modern Olympics.
This is the Tholos at the sanctuary of Athena Pronaia, a circular building that was constructed between 380 and 360 BC. It consisted of 20 Doric columns arranged with an exterior diameter of 14.76 meters, with 10 Corinthian columns in the interior.
The Tholos is located approximately a half-mile (800 m) from the main ruins at Delphi. Three of the Doric columns have been restored, making it the most popular site at Delphi for tourists to take photographs.