Delphi was one of the most important cities of Ancient Greece. It is sited among mountains close to a spring that was supposed have special powers.
Delphi was famous as the place where there was an oracle - a person who went into a trance and told the future. As the Ancient Greeks were very supersticious, even generals would come to the oracle before a battle to seek advice. People now think that the oracle went in to a trance becasue she sat in a room which was over a supply of fumes that came up naturally from the rocks.