Yeah they are both ancient kingdoms built up over time. They hate one another because not only are they exact opposites in beliefs, but there has always been border issues.

Oh by the by, the North kingdom is a large castle that once was a fortress, branching out, the city spilling out of the walls, so a second wall was created for protection.

The Southern kingdom's palace was built high on a cliff and even in the cilff, but is in sections since their culture was build around the keeping of peace and honoring of the Goddesses, instead of war.