The sanctuary of Delphi, the most popular oracle of ancient Greece, is located in the slopes of Mount Parnassus, in the natural landscape formed between two rock formations, the Phaedriades. The origins of Delphi are lost in prehistory. According to Greek mythology, Delphi was the center of the world then. Zeus, king of gods and humans, wanted to find out where the center of the world was. So he released two eagles, one to the west and the other to the east, and then placed a stone monument named Omphalos, meaning navel, at the place where they crossed paths in Delphi. At first, the site was dedicated to the mother goddess of the earth here. It was protected by a big snake named Python. Apollo, god of the sun and light, son of Zeus and Leto, and twin brother of Artemis, goddess of hunting, killed this snake with his arrow and buried it there. Then he sat on the top of Mount Parnassus, looking out at the Aegean Sea, and as he was looking, he saw a ship that had just left from Knossos, on the island of Crete. He turned himself into a dolphin and swam next to the ship, guiding it towards Delphi. The god Apollo revealed himself to the Cretans aboard the ship and announced that he had selected them to become the priests of his temples. Indeed, both Apollo's cult and the sanctuary of Delphi came from the Cretans.