The city was along the Seyhan River in the ancient past and probably in marine contact with the Sea. Tarsus sits on the east side of the Cilician Gates and controlled all trade by this route. Control of the Cilician plain, as the hinge point of routes, controlled trade to Israel and Egypt, from Europe.

Tarsus, 14 miles east of Mersin, was indeed the largest city in Cilicia in ancient times. It was an unpretentious town, with narrow, tortuous streets, mud houses, and a small bazaar. Today no spectacular remains exist to give evidence of the former importance of the very ancient town.

Tarsus, the chief town of Cilicia, and the birthplace and early residence of the apostle Paul, known then as Saul of Tarsus.

St Paul took refuge in Tarsus after his conversion, and was later joined by Barnabas. It is possible that this was the beginning of the Christian community of Tarsus, but it is not known for sure. The first known bishop of Tarsus, Helenus, dates from the third century. Records show that he went several times to Antioch during the dispute with Paul of Samosata. Others include Lupus, present at the Council of Ancyra in 314; Theodorus, at that of Nicaea in 325; Helladius, condemned at Ephesus, and who appealed to the pope in 433.