The Stone Gardens was a region just east of Undertown, at the farthest tip of the Edge. During the Quint and Twig trilogies, buoyant rocks grew in the Stone Gardens, pushing up rocks above and creating rock stacks. The White Ravens resided there and screeched when it was time to harvest the rocks for use in sky ships, which, combined with the eerie howls of ripe rocks, was known as the Chorus of the Dead, a noise which spooked the inhabitants of Undertown so badly that businesses often remained closed on mornings when a new batch of rocks was ready to be harvested. The academics of Sanctaphrax jealously guarded their right to harvest the buoyant rocks. Trespassing in the Stone Gardens was punishable by death, though few Undertowners would have dared to venture there anyway, with the exception of desperate rubble-scroungers.
Four years after the events of Midnight Over Sanctaphrax, Stone-Sickness struck the Edge, and the Stone Gardens ceased to produce buoyant rocks. The stacks began to tumble and fall and soon all that remained were a number rocks in ruins.
During the events of The Immortals, Sanctaphrax was blown back to the Edge, and hovered over the Stone Gardens. Stone-Sickness was then cured by the destruction of the Gloamglozers, and buoyant rocks began to grow again.