Greek myth holds that the thunder god Zeus once dispatched two eagles flying in opposite directions across the sky. Where their paths crossed would be the center of the world. Legend says that the birds met over Delphi, seated on the slopes of Parnassós. Zeus marked the spot with a stone called the omphalos (navel), to signify the location’s centrality.
According to another myth, this impressive spot in central Greece (about 100 miles northwest of Athens) was originally sacred to Gaea, mother goddess of the earth, who placed her son Python, a serpent, as a guard for Delphi and its oracle. Apollo, god of light and music, slew the serpent and took over the site for himself. Priestesses who served Apollo there were called the “Pythia,” named in honor of Gaea’s vanquished son. Throughout the classical world spread the belief that these priestesses channeled prophecies from Apollo himself. (Read about the science behind the Delphic Oracle's prophetic powers.)
The cult of Apollo seems to have been functioning in Delphi as early as the eighth century B.C. About two centuries later, leaders from all over Greece were consulting the oracle on major issues of the day: waging war, founding colonies, and religious rituals. Since it was a place used by different—and often rival—Greek states, Delphi soon became not only a sacred space but also a place where a city-state could exhibit its status to the wider Greek world.