I read a fascinating book about the Vikings recently that touched on this topic.
One really interesting tidbit was the route they took.[0] At first blush, I'd expect them to have sailed/rowed their longboats counter-clockwise around Europe, through the straights of Gibraltar and into the Med. But they actually took much more direct route--straight through Europe! They'd go east through the Baltic Sea, up a navigable river like the Daugava to a point where that river neared the Dneiper river, at which point they'd jump out and hump their boats down to the Dneiper, which would carry them to the Black Sea.
One really interesting tidbit was the route they took.[0] At first blush, I'd expect them to have sailed/rowed their longboats counter-clockwise around Europe, through the straights of Gibraltar and into the Med. But they actually took much more direct route--straight through Europe! They'd go east through the Baltic Sea, up a navigable river like the Daugava to a point where that river neared the Dneiper river, at which point they'd jump out and hump their boats down to the Dneiper, which would carry them to the Black Sea.
The world has small for a very long time.
[0] https://en.wikipedia.org/wiki/Route_from_the_Varangians_to_t...