Atlantinopolis

Atlantinopolis is a city from the planet Moebius, located on the Sunken Island. It is an alternate version of Echidnaopolis, but is uninhabited except for Anti-Knuckles. It was threatened with destruction by Dr. Robotnik and Evil Sonic when they tried to steal its Chaos Emeralds, but thanks to the Knothole Freedom Fighters and Knuckles Prime the city was saved. It was presumably either conquered or destroyed by Scourge the Hedgehog when he battled Anti-Knuckles. (StH: #44, #193)