At an estimated 24, 000 seating capacity, the 'Theatre at Ephesus, is believed to be the largest outdoor theatre in the ancient world. Ephesus was an ancient Greek city southwest of present-day Seljuk, in zmir Province, Turkey. It was built in the 10th century BC on the site of the former Arzawan capital, by Attic and Ionian Greek colonists. During the Classical Greek era it was one of the twelve cities of the Ionian League. The city flourished after it came under the control of the Roman Republic in 129 BC.