And then things get interesting when a fleet of trimarans slide onto the beach of the impassable sea.They don't know. The area where my series takes place has three countries (using the loosest possible definition; it's effectively Germanic tribal law holding strings of held territories in alignment), an elf sanctuary/homeland that many believe is only a rumor, one breakaway republic who may or may not belong to one of the countries depending on whom you ask, and a couple of principalities owned by the largest country that have the same problems as everybody else: a limited rule of law. The outlying areas are teetering on the edge of administrative collapse, and it gets more factious the further you drift from the seats of power. Way out in the hinterlands, it's basically Somalia with swords.
That said, it's surrounded on three sides by mountains and the fourth by an impassable sea, with one small bottleneck leading to a desert, and no one has any clue what's on the other side. To them, this little corner of the planet (they don't even know it's a planet) is "the world," but it's about the size of Montana. Nobody who ventures over the far mountains, into the desert, or out into the sea ever comes back. And nobody ever comes from there. And that's fine with them.