Ephesus ist the most interesting ancient greek city besides the greek mainland. See the Library of Celsus and the Temple of Artemis (550 BC), one of the Seven Wonders of the Ancient World. Very impressive for it's accustics is the great theather (capacity for more than 24,000 people). Festivals are celebrated nowadays. See the House of Virgin Mary in Selcuk if you are intersted in early christian history. It is a very impressive ancient town constructed by ionians, greeks, ruled by romans, and a lot of archeological activities and findings is still going on ...