BirdieMaps has created this spectacular sewer battle map which would work perfectly beneath Ptolus. They created it with a thief hideout in mind, but this could easily be a ratman nest for your City by the Spire Campaign. Download the large version of the map completely free. Consider supporting BirdieMaps on Patreon.

Sewer System Huge Thief Hideout Thieves Lair Ratmen Rat Men Ptolus Birdie Maps Sewers Dungeon Battle Map Grid DND Dungeons Dragons Pathfinder D20

Download Full Size Sewer Battle Map