For over a thousand years, the Oracle of Delphi was the most prestigious religious site in Greece. A priestess known as the Pythia would enter a trance (likely aided by hallucinogenic ethylene gases rising from a geological fault) and deliver cryptic prophecies believed to be the words of the god Apollo. Kings and commoners alike traveled there before making major decisions, such as going to war or founding a colony. The prophecies were notoriously ambiguous; when King Croesus of Lydia asked if he should attack Persia, the Oracle told him he would 'destroy a great empire.' He attacked, but the empire he destroyed was his own. The site remains a symbol of the Greek belief in fate and the complex relationship between divine will and human agency.