Didyma- Temple of Apollo

Located about 11 miles south of the ancient port city of Miletus on the western coast of modern-day Turkey, the Temple of Apollo at Didyma or Didymaion was the fourth largest temple in the ancient Greek world. The temple’s oracle, second in importance only to that at Delphi, played a significant role in the religious and political life of both Miletus and the greater Mediterranean world; many rulers, from Alexander the Great (356-323 BCE) to the Roman emperor Diocletian (244-313 CE) visited or sent delegations to this oracle seeking the guidance and favor of Apollo. The oracle played a significant role in initiating the “Great Persecution” of Christians under Diocletian and the temple was later converted into a church during the 5th or 6th century CE.
(www.ancient.eu)