Since ancient times, ships from the east (Asia Minor, Syria, Phoenicia, and Egypt) and the west (Italy and Spain) came with their cargoes, unloaded them at one harbor, and transported them the few miles overland to the other side of the isthmus.
Ja kravu bija paredzēts vest tālāk, ostā preces izkrāva no kuģiem un pa sauszemi pārveda pāri Istmam uz ostu pretējā krastā. Tur preces iekrāva citos kuģos, un to ceļš turpinājās.