Chasm City was the largest settlement on Yellowstone, easily dwarfing Ferrisville, the second largest. When Americans originally settled the Epsilon Eridani system by Von Neumann robot, the location of Chasm City -- a huge crater spewing unusual gases -- was spotted. The crater's edges granted protection from the wind storms and its gases helped provide a breathable atmosphere for the original colony, and for the city that would come later, which was contained underneath eighteen huge bio-domes known collectively as "The Mosquito Net".