@christym- Delphi is one of the most popular sites, in an archaeology sense, in Greece. The Oracle of Delphi was known as the most important shrine in Greece. It dates back to 1400 BC. It was considered the center (omphalos) of the world.
At the time, the priestess of Apollo, Pythia, was the person to see if you had a question about the future. Her answers were considered as truth. Major decisions would be made based off her words.
One example of an oracle is the prediction of the Battle of Salamis. It is said that Pythia predicted doom and that a wooden wall of some type would save them. The wooden wall was interpreted to be a ship.
When asked to define soothsayer, the Oracle at Delphi is the first thing that comes to my mind.