
Delphi is primarily famous as a shrine to Apollo and for its Oracle. A priestess of Apollo, called the Pthia, would sit in a grotto and under the influence of foul smelling, intoxicating gasses she would come up with predictions of the future - this is the site where Oedipus was told his terrible fate and Socrates that there was no man wiser than he! The oracle had a reputation of making TRUE but very obscure pronouncements.
Over the main entrance was enscribed the legend that Socrates put so much stock in "Know Thyself" [Originally meaning something like "Know thy place" but after Socrates it usually takes its current meaning.)
The primary oracle was the Pythia, speaking for Apollo, but for one month of the year the Dyionisian oracle held sway. Her title comes down to us as the English "Pithy" as in a "Pithy saying". The town had a number of oraclular traditions, but those two were the ones that were considered "authoritative".
The pythia is gone of course, and the original grotto, although the grotto where pilgrams cleaned and purified themselves remains. There are temples, there is a running track (the Pythian games of Delhi were almost as important as the Olympics) and a lot of columns.
Delphi is perched on a mountain, with a spectacular set of views who's beauty has been remarked on from ancient times to modern.
The name Delphi has the same root word as the modern English "Dolphin", and refers to Apollo coming to the site originally (down by the port, of course) in the form of a dolphin.
The oracle of Delphi operated for farther back than we have records, and the final recorded pronouncement was that given to Justin the Apostate when he tried to revive the old religion in the face of the growing Christian churches. That pronouncement (known by heart by most Greeks) was the death stroke for the old religion.
Delphi was also considered by the ancients as the "center of the world" and there was a stone that marked the exact spot.
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