Cartography shows that the Isthmus of Tehuantepec used as inter-oceanic passage

Google Maps link with a pin roughly where you might leave the river to travel further south: https://goo.gl/maps/yEeRXqyToC1JYV2Q6

Very interesting. From the article, 220km is the shortest between the two oceans in today's Mexico region, and two thirds of it were done along the river Coatzacoalcos, the rest overland.

In comparison, a commonly-used portage in Greece was only 8km long: https://en.wikipedia.org/wiki/Diolkos

Much less work, but of course much less benefit.

>> the ancient trade and military route located on the shortest distance (ca. 70 kilometers)

https://en.wikipedia.org/wiki/Don%E2%80%93Volga_portage

Wow, that was used for a long time. The Greek one was 700 years.

There is another in North America that was used for thousands of years before the French found it:

https://en.wikipedia.org/wiki/Chicago_Portage