The town was important and prosperous due to its river crossing, which allowed east-west land traffic to pass through it.
More recently it has been suggested that Thapsacus was renamed to Seleucia at the Zeugma, which lies further upstream on the Euphrates.
[1] The Greek geographer Eratosthenes, who lived during the third and second century BC, gave a distance of 4,800 stades from Thapsacus to Babylon through the route along the Euphrates.
[6] The continued importance of the city is the reason Eratosthenes choose Thapsakos as one of the reference points for his system of latitude and longitude.
Thapsakos' identification with Europos (the Hellenistic name of Carchemish) finds some support from a corrupt passage in Plinius' Naturalis Historia.
[7] "And in Syria [it flows past the following] towns: Europus formerly Thapsacus, now Amphipolis, the Tent-Dwelling Arabs.