The Delphic Oracle of Apollo
The Oracle at Delphi under the tutelage of Apollo, the god of reason  was the most famous of such centers. The answers to the pilgrim’s questions were channeled through priestesses called Pythia. The Pythia first cleansed herself in a spring with sacred waters, then drank from another spring with sacred waters and sat next to the Omphalos stone until she entered in a trance. In this state she received the answer from Apollo, which she transmitted to the pilgrim.

From documents that survive we see that the answers were actually warnings or council that the receiver could rarely interpret properly because of his ego. When the Oracle predicted that Troy would be destroyed by King Laios’ son Paris, the king’s reaction was to send child away. It wasn’t the son who destroyed the city - it was the father’s predicable response according to the way he dealt with life’s conflicts that brought down Troy. The Oracle was simply bringing to the surface a person’s life pattern and its consequences based on the laws of cause and effect. While he thinks he’s solved the problem by abandoning his son, in reality he’s carrying out his destiny.

The historian Herodotus relates around a hundred verses where the message is one of wisdom and humility. Unfortunately - or predictably - politics infiltrated the sacred lieu which led to a propaganda war that eventually discredited the centers.

According to the historian Diogene Laerce, a group of philosophers decided to visit the Oracle at Delphi. They were received with great honors and were each asked to engrave a maxim on the temple walls. Chilone, a philosopher from Sparta, is said to have written the most famous above the entrance: Know thyself. Thales wrote his maxim on the corner of the temple, where pilgrims could see it in passing: "Remember your friends".

Prophesizing has existed in every culture, apparently as far back as 3000 BC. Astrology was a popular form of divination in China and Mesopotamia around 2000 BC. From the start people looked for signs to orient their lives.

Actual centers where people came to solicit predictions appeared in Greece around the 5th century BC. Beautiful temples were built to honor different gods and functioned as a religious community. The word Oracle stems from the Latin word orare,  “to speak.”