The largest and most important port in the eastern Mediterranean during the time of Jesus Christ (roughly the 1st century CE) was
Alexandria, Egypt.
While other ports like Caesarea Maritima (in Judea) and Ephesus (in Asia Minor) were significant, Alexandria was a major center of trade, culture, and Hellenistic learning, making it the dominant port in the region. Its location, its harbor facilities, and its connections to the Nile River and the vast Egyptian hinterland gave it a considerable advantage.