Ephesus was an ancient Greek city located in present-day Turkey. It was one of the most important cities of the Roman Empire and was known for its well-preserved ruins, including the Temple of Artemis (one of the Seven Wonders of the Ancient World) and the Library of Celsus. It was also an important center of early Christianity and the site of the Third Ecumenical Council of 431 AD. Visitors to Ephesus can explore the ancient city’s streets, theater, and public buildings, as well as several early Christian churches. Today, it is a UNESCO World Heritage site.