Delphi - Oracle
The first oracle at Delphi was commonly known as Sibyl or Pythia, though her name was Herophile. She sang her predictions, which she received from Gaia. Later, "Sibyl" became a title given to whichever priestess manned the oracle at the time. The Sibyl sat on the Sibylline Rock, breathing in vapors from the ground1 and gaining her often puzzling predictions from that. Pausanias claimed that the Sibyl was "born between man and goddess, daughter of sea monsters and an immortal nymph". Others said she was sister or daughter to Apollo. Still others claimed the Sibyl received her powers from Gaia originally, who passed the oracle to Themis, who passed it to Phoebe.

This oracle exerted considerable influence across the country, and was consulted before all major undertakings: wars, the founding of colonies, and so forth. She also was respected by the semi-Hellenic countries around the Greek world, such as Lydia, Caria, and even Egypt. Croesus of Lydia consulted Delphi before attacking Persia, and according to Herodotus received the answer "if you do, you will destroy a great empire." Croesus found the response favorable and attacked, and was utterly overthrown (resulting, of course, in the destruction of his own empire).

The oracle is also said to have proclaimed Socrates the wisest man in Greece, to which Socrates said that if so, this was because he alone was aware of his own ignorance. This claim is related to one of the most famous mottos of Delphi, which Socrates said he learned there, Gnothi Seauton (Γνώθι Σεαυτόν): "know thyself". Another famous motto of Delphi is Meden Agan (Μηδέν Άγαν): "nothing in excess".

In the 3rd century A.D., the oracle (perhaps bribed) declared that the god would no longer speak there.

The temple to Apollo at Delphi was built by Trophonius and Agamedes.