The Oracle gives the builder one free technology advance, and it increases the odds of its city generating a Great Prophet.
In ancient Greek religion, an oracle was a priest or priestess through whom the gods spoke in response to questions. The oracle interpreted dreams, the actions of entranced persons, and physical signs found in the entrails of sacrificed animals. The most famous oracle resided in the shrine of Apollo at Delphi, located on the slopes of Mount Parnassus. Greeks, Romans, and others consulted this oracle for centuries about public policy and private matters. A priestess called the Pythia would, for a fee, make public predictions for the future. These ecstatic pronouncements became infamous for their ambiguity.