Aridhol from it's description was just as big as Caemlyn or Tanchico.

Also, medieval peasants aren't reliant on transnational trade. Even if trade routes collapsed and political anarchy reigned causing the collapse of urban civilization within a nation the peasants should still remain as long as the land is fertile, and as far as we know the Caralain grass and the other abandonded regions still are. Early Medieval Germany had only a handful of cities larger than Baerlon but that didn't mean there weren't lots of peasant villages scattered across the land. Even the Black Forest wasn't as unpopulated as people think.