The belt is a place along the coast, at the far side of the island, where all the garbage is dumped into the water below. It has grown into a mound that runs all the way to the bottom of the sea. In it scavengers, both animal and human, roam unchecked. Rats, mainly.
The sewers end up here as well.
It is a most filthy place. Most people stay away from this part of the island. Which makes it a good place for merchants and hustlers who don't want any interference while conducting their trade.