Ephesus was one of the greatest cities of the Roman Empire, surpassed only by Rome, Alexandria, and Antioch. The population in Paul's day is estimated at 250,000. It became the capital of Asia Minor in 27 B.C. And served as the center of proconsular government. On inscriptions, Ephesus is referred to as the greatest metropolis of Asia.
Ephesus was strategically located at the center of commerce between East and West. As the Roman Empire stretched across the Mediterranean, Ephesus' large and sheltered harbor became more important. Interesting, it was her harbor that later led to the later decline of Ephesus. The harbor was narrow and shallow and was prone to silting and required regular dredging to keep the passage open. Today Ephesus lies 4 miles from the sea.
Long before the coming of the Romans, Ephesus was celebrated as the center of worship of the goddess Artemis. A thriving tourism and pilgrim trade existed as devotees from throughout the Mediterranean world came to worship at the Artemisium, or great temple of Artemis. This temple was originally built in the 6th century BC and rebuilt in massive proportions two hundred years later to make it reputedly four times the size of the Parthenon in Athens and considered to be one of the seven wonders of the world.
Artemis was an ancient goddess of fertility. Pilgrims came to her temple seeking aid in becoming pregnant and protection in childbirth. A college of virgin priestesses served her. The devotion of the city to their goddess earned the Ephesians the title "temple-keeper." Religious fervor, along with the very real economic dependence of the city on the pilgrim trade, led to a near riot on behalf of Artemis as described in Acts 19:23-41 where the 25,000 seat theatre was filled with fevered citizens shouting repeatedly "Great is Artemis of the Ephesians!"