Delphi is perhaps best known for its oracle, the Pythia, the sibyl or priestess at the sanctuary dedicated to Apollo.
According to Aeschylus in the prologue of the Eumenides, the oracle had origins in prehistoric times and the worship of Gaea, a view echoed by H.W. Parke.

One tale of the sanctuary's discovery states that a goatherd, who grazed his flocks on Parnassus, one day observed his goats playing with great agility upon nearing a chasm in the rock; the goatherd noticing this held his head over the chasm causing the fumes to go to his brain; throwing him into a strange trance.

Apollo spoke through his oracle.
She had to be an older woman of blameless life chosen from among the peasants of the area.
Alone in an enclosed inner sanctum (Ancient Greek adyton - "do not enter") she sat on a tripod seat over an opening in the earth (the "chasm").
According to legend, when Apollo slew Python its body fell into this fissure and fumes arose from its decomposing body.
Intoxicated by the vapours, the sibyl would fall into a trance, allowing Apollo to possess her spirit.
In this state she prophesied.
The oracle could not be consulted during the winter months, for this was traditionally the time when Apollo would live among the Hyperboreans.
Dionysus would inhabit the temple during his absence.

The time to consult pythia for an oracle during the year is determined from astronomical and geological grounds related to the constellations of Lyra and Cygnus but the hydrocarbon vapours emitted from the chasm.
Similar practice was followed in other Apollo oracles too.

While in a trance the Pythia "raved" – probably a form of ecstatic speech – and her ravings were "translated" by the priests of the temple into elegant hexameters.
It has been speculated that the ancient writers, including Plutarch who had worked as a priest at Delphi, were correct in attributing the oracular effects to the sweet-smelling pneuma (Ancient Greek for breath, wind or vapour) escaping from the chasm in the rock.
That exhalation could have been high in the known anaesthetic and sweet-smelling ethylene or other hydrocarbons such as ethane known to produce violent trances.
Though this theory remains debatable the authors put up a detailed answer to their critics.

Ancient sources describe the priestess using “laurel” to inspire her prophecies.
Several alternative plant candidates have been suggested including Cannabis, Hyoscyamus, Rhododendron and Oleander.
Harissis claims that a review of contemporary toxicological literature indicates that oleander causes symptoms similar to those shown by the Pythia, and his study of ancient texts shows that oleander was often included under the term "laurel".
The Pythia may have chewed oleander leaves and inhaled their smoke prior to her oracular pronouncements and sometimes dying from the toxicity.
The toxic substances of oleander resulted in symptoms similar to those of epilepsy, the “sacred disease,” which may have been seen as the possession of the Pythia by the spirit of Apollo.

The Delphic oracle exerted considerable influence throughout the Greek world, and she was consulted before all major undertakings including wars and the founding of colonies.
She also was respected by the Greek-influenced countries around the periphery of the Greek world, such as Lydia, Caria, and even Egypt.

The oracle was also known to the early Romans.
Rome's seventh and last king, Lucius Tarquinius Superbus, after witnessing a snake near his palace, sent a delegation including two of his sons to consult the oracle.

In 83 BCE a Thracian tribe raided Delphi, burned the temple, plundered the sanctuary and stole the "unquenchable fire" from the altar.
During the raid, part of the temple roof collapsed.
The same year, the temple was severely damaged by an earthquake, thus it fell into decay and the surrounding area became impoverished.
The sparse local population led to difficulties in filling the posts required.
The oracle's credibility waned due to doubtful predictions.

The oracle flourished again in the second century CE during the rule of empero
Delphi is perhaps best known for its oracle, the Pythia, the sibyl or priestess at the sanctuary dedicated to Apollo. According to Aeschylus in the prologue of the Eumenides, the oracle had origins in prehistoric times and the worship of Gaea, a view echoed by H.W. Parke.
One tale of the sanctuary's discovery states that a goatherd, who grazed his flocks on Parnassus, one day observed his goats playing with great agility upon nearing a chasm in the rock; the goatherd noticing this held his head over the chasm causing the fumes to go to his brain; throwing him into a strange trance.
Apollo spoke through his oracle. She had to be an older woman of blameless life chosen from among the peasants of the area. Alone in an enclosed inner sanctum (Ancient Greek adyton - "do not enter") she sat on a tripod seat over an opening in the earth (the "chasm"). According to legend, when Apollo slew Python its body fell into this fissure and fumes arose from its decomposing body. Intoxicated by the vapours, the sibyl would fall into a trance, allowing Apollo to possess her spirit. In this state she prophesied. The oracle could not be consulted during the winter months, for this was traditionally the time when Apollo would live among the Hyperboreans. Dionysus would inhabit the temple during his absence.
The time to consult pythia for an oracle during the year is determined from astronomical and geological grounds related to the constellations of Lyra and Cygnus but the hydrocarbon vapours emitted from the chasm. Similar practice was followed in other Apollo oracles too.
While in a trance the Pythia "raved" – probably a form of ecstatic speech – and her ravings were "translated" by the priests of the temple into elegant hexameters. It has been speculated that the ancient writers, including Plutarch who had worked as a priest at Delphi, were correct in attributing the oracular effects to the sweet-smelling pneuma (Ancient Greek for breath, wind or vapour) escaping from the chasm in the rock. That exhalation could have been high in the known anaesthetic and sweet-smelling ethylene or other hydrocarbons such as ethane known to produce violent trances. Though this theory remains debatable the authors put up a detailed answer to their critics.
Ancient sources describe the priestess using “laurel” to inspire her prophecies. Several alternative plant candidates have been suggested including Cannabis, Hyoscyamus, Rhododendron and Oleander. Harissis claims that a review of contemporary toxicological literature indicates that oleander causes symptoms similar to those shown by the Pythia, and his study of ancient texts shows that oleander was often included under the term "laurel". The Pythia may have chewed oleander leaves and inhaled their smoke prior to her oracular pronouncements and sometimes dying from the toxicity. The toxic substances of oleander resulted in symptoms similar to those of epilepsy, the “sacred disease,” which may have been seen as the possession of the Pythia by the spirit of Apollo.
The Delphic oracle exerted considerable influence throughout the Greek world, and she was consulted before all major undertakings including wars and the founding of colonies. She also was respected by the Greek-influenced countries around the periphery of the Greek world, such as Lydia, Caria, and even Egypt.
The oracle was also known to the early Romans. Rome's seventh and last king, Lucius Tarquinius Superbus, after witnessing a snake near his palace, sent a delegation including two of his sons to consult the oracle.
In 83 BCE a Thracian tribe raided Delphi, burned the temple, plundered the sanctuary and stole the "unquenchable fire" from the altar. During the raid, part of the temple roof collapsed. The same year, the temple was severely damaged by an earthquake, thus it fell into decay and the surrounding area became impoverished. The sparse local population led to difficulties in filling the posts required. The oracle's credibility waned due to doubtful predictions.
The oracle flourished again in the second century CE during the rule of empero
Delphi