Tephra Terraces

The city's wealth primarily comes from their extensive cultivation of a number of otherwise rare herbs and mushrooms found throughout the Obsidian Peaks, which are sold at high prices through Aerius and even traded to aliens up in Galactica by some of their buyers.  While they eschew the lava canals of Caldera, their solution to avoid eruptions that might damage their precious harvests have been to dig and manage lava pools, and to even transport lava to create new landforms or fanciful sculptures as it cools.  (Naturally, the unique sculptures are another source of the city's wealth).