Continuing with last week's mythological theme of prophecy and fatalism in ancient Greek thought, I would be remiss if I didn't mention the Oracle of Delphi. The Oracle was not only the best-known prognosticator in the Greek world, but one of its major institutions as well. It had a reputation for never being wrong, although that was generally accomplished by giving vague advice that could mean multiple things. One of the most famous examples involved the Battle of Salamis, before which the Athenians were told to put their faith in "wooden walls." They took this to mean their naval fleet, and were able to defeat the Persians. The Oracle was said to have started up in the eighth century BC, and while the institution lost popularity during Roman times, it continued until Emperor Theodosius ordered a general shutdown of pagan temples in 393 AD.
While sources indicate that the site of Delphi was regarded as sacred to Gaia and Poseidon in its earlier days, it's Apollo who was generally said to have been in charge of the Oracle. It's where the solar deity is said to have killed the serpent Python, one of the monstrous offspring of Gaia, and the relentless pursuer of his mother Leto. It's interesting that "Python" is an anagram of "Typhon," another primordial monster of Greek legend. Not that this is the case in Greek, but they might well have had similar roots anyway. Anyway, since Python was the child of the Earth Goddess, Apollo had to perform menial tasks as penance for the killing. The rotting corpse of Python remained at Delphi, and its fumes were sometimes said to have put the priestess, or Pythia, into a trance. Apollo is also said to have brought the first people to the site in the form of a dolphin, hence the name "Delphi."
While I'm not sure there's any concrete proof of how the Oracle operated, and perhaps it changed over time, a common view is that the Pythia went into a trance caused by intoxicating gases, and basically muttered gibberish. A priest would then translate the babbling into poetic Greek, resulting in the famous pronouncements. It's been noted that this is pretty similar to shamanic practices, making it yet another case of poison or drugs said to bring a person closer to the gods.
Delphi is also one of the popular sites designated as the center of the world by ancient Greeks, and I believe it is more or less equidistant from several other important holy places. The bit about Apollo turning into a dolphin is generally regarded as a folk etymology, with "Delphi" probably actually originating from the term for "womb." In other words, before it came to be associated with Apollo, it might well have been regarded as Gaia's womb. It was also the location of the Omphalos stone, which means "navel." It wouldn't make too much sense for the Earth Goddess' womb and belly button to be in the same place, but both designations indicate that this was a significant part of the world.