An egg-shaped ice structure in the Ice Cap Zone where Doctor Robotnik was testing his Inter-Zone portal technology. From here, Robotnik would send squadrons of Badniks on the Floating Island through the Inter-Zone gateway to attack different Zones on Mobius. Sonic and Knuckles discovered this outpost and broke in, only to be trapped inside a laser barrier. Knuckles managed to dig them under and out of the barrier and the two heroes destroyed the structure along with the Inter-Zone gateway.