Toxic Caves is a disgusting, slimy dungeon, filled to the brim (literally) with horrible green ooze which is all kinds o' deadly. The level encompasses the half-submerged caves at the foot of Mt. Mobius, where Sonic washes up after being blasted off the Tornado during his and Tails's approach to the Veg-O-Fortress. In keeping with Eggman's general ethos regarding environmentalism, the fat man is using the caves as a dumping ground for kilotons of radioactive slurry produced by the Fortress' cruel industry. Rusted sewer pipes snake through rocks dripping with fluorescent green pollution, and the waters below are patrolled by an immense robotic sea-serpent.