Barbaricum

Back on the continent, the border ran from the North Sea through the southwestern corner of the Netherlands.

Nijmegen, the site of a massive battle involving American and British paratroopers in World War II, was just a few miles from Barbaricum, what the Romans called the land beyond the borders, the land of the barbarians.

From there, the border ran into the very western piece of modern-day Germany.

Neuss, Cologne, and Bonn were military border cities.