Asteroid fields were located at the edge of Nevarro's system. The fields were mined by by belters, and the money made from mining them helped Nevarro City on the planet Nevarro to prosper.
After Din Djarin shot pirates from Gorian Shard's pirate gang on Nevarro, the gang ambushed him at the asteroid fields. Djarin was able to destroy several of the pirates' fighters, until he was led to Gorian Shard's Corsair, and escaped.