The ruins at Ephesus are the best preserved of the Roman ruins in the Mediterranean. It it close to the town of Selcuk in southern Turkey, and the closest airport is Izmir about 70 km away. Not meaning to sound like a travel guide, but I think the best way to get around is to rent a car from the airport.
Ephesus was founded by the Greeks and became a city and port with a population of 200,000 under their influence. The city came under Roman control in 2nd century BC and later became a centre for Christianity. Only about 10% of this ancient town has been excavated so far. Most of the ruins are the legacy of the Romans.
The highlight of Ephesus now is the facade of Celcus Library - reconstructed from the original ruins. It is best viewed in the morning sun.