From Wikipedia

Delphi

In Greek mythology, Delphi was the site of the Delphic oracle, the most important oracle in the classical Greek world, and 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. Python (derived from the verb pythein, "to rot") is claimed by some to be the original name of the site in recognition of the Python that Apollo defeated (Miller, 95). The Homeric Hymn to Delphic Apollo recalled that the ancient name of this site had been Krisa.

 Apollo's sacred precinct in Delphi was a panhellenic sanctuary, where every four years, starting in 586 BC (Miller, 96) athletes from all over the Greek world competed in the Pythian Games, one of the four panhellenic (or stephanitic) games, precursors of the Modern Olympics. The victors at Delphi were presented with a laurel crown which was ceremonially cut from a tree in Tempe by a boy who re-enacted the slaying of the Python (Miller, 96). Delphi was set apart from the other games sites because it hosted the mousikos agon, musical competitions (Miller, 95). These Pythian Games rank second among the four stephanitic games chronologically and based on importance (Miller, 96). These games, though, were different from the games at Olympia in that they were not of such vast Importance to the city of Delphi as the games at Olympia were to the city of Olympia. Delphi would have been a renowned city whether or not it hosted these games; it had other attractions that led to it being labeled the "omphalos" (navel) of the earth, in other words, the center of the world .