"Yeah, they claim the Vikings went all the way down to the Caspian, via river passage and portage, trading furs (for kittens."
Those would be Swedes.
The ones that conquered southern Italy were Norwegians, relatives of William the Conqueror. Presumably came around via Atlantic.
The richest stores of mediterranean Amber were found, on an island off Sweden, I seem to recall.
Weren't the Vikings from both Norway and Sweden? Those countries didn't exist as separate states back then. My forefathers were Vikings who went to Ireland via Normandy.