The church is situated on the north of the Harbor Baths. Its main entrance is at the Koressos Gate in the direction of Selçuk-Kuşadası highway. This church, one of the important edifices of Christianity, is the first church which was dedicated to Virgin Mary.The third meeting of the Ecumenical Council was held in this church in A.D 431. It was built in the 2nd century as a Museion and it measures 260m. by 30m. In the museion higher education was applied and medicine and other sciences were taught. Besides, the priests who occupied important positions at Ephesus were also trained here.