In the ancient world, the Delphic Oracle was considered to be the most accurate means by which predictions and prophecies could be made. It was located at the Temple of Apollo in Delphi.
Even today, the ruins of the legendary Temple can be seen on the slopes of Mount Parnassus.
The Temple dedicated to the god Apollo was built in his honor after his triumphant victory over the monster Python. The main priestess in the Temple was called Pythia, while the python became one of the symbols of Apollo.
In ancient Greece, all statesmen would consult the oracle before making an important state decision, with the Oracle at Delphi thus predetermining the politics in antiquity.
Initially, prophecies were only made once a year - on Apollo's birthday, which was in the middle of February or March, according to the different sources.
Later on however, prophecies were made every month on the 7th. Only the priestess Pythia was able to prophesize with the Oracle. She would refuse to predict the future of people who committed an excessive number of crimes. The priestess required full devotion and deep virtues.
For every prophetic vision, Pythia would wash in the Castalian Spring, put on golden clothing, let her hair loose and place a laurel wreath on her head. The priestess would then sit in a high three-legged chair, drink water from the holy spring, light laurel branches on fire, breathe in their fumes and make her predictions.
Pythia would fall into a drug-induced ecstasy and everything she said had to immediately be written down and interpreted later. After interpretation, the prophecy was always presented in the form of a poem to the one seeking it.
The inside of the temple at Delphi was restricted to regular people and only the priestesses could enter inside. Near the Oracle at Delphi, there stood a golden statue of Apollo, a laurel tree, a holy spring, an omphalos with 2 golden eagles, and under it, a sarcophagus with the ashes of the monster Python.
According to Plutarch, who was also once a priest at the Temple of Apollo, the prophetic power of Pythia was due to the breathing in of some kind of mysterious fumes, coming from the bowels of the earth. However, geologists' investigations have not found such gases.