New Mobotropolis is a city that exists within the Archie Comics continuity of Sonic the Hedgehog. It is the current home of the Knothole Freedom Fighters and seat of power for the Republic of Acorn. The city was originally created by Dr. Eggman's renegade tactical AI, A.D.A.M. and looked nothing like it does now. A.D.A.M. had constructed the city entirely out of microscopic nanites and had intended to let these nanites continouously reproduce and build new structures until they eventually overwhelmed the whole planet. Thanks to Sonic the Hedgehog and the Freedom Fighters, A.D.A.M. discontinued the nanite's advance. For months, the nanite city remained dormant and empty, but following the Eggman Empire's bombardment of Knothole City, the Republic of Acorn was forced to relocate. Sally Acorn's companion AI NICOLE interfaced with the nanite city, re-awakening the microscopic machines and taking full control of them. NICOLE used the nanites to reconfigure the city and create a perfect replica of Mobotropolis, the old capital of the kingdom before Robotnik Prime had turned it into Robotropolis. Since then, the Republic has endured and lived in safety from Dr. Eggman's tyranny.
NICOLE is capable of restructuring any part of the city at will and has used this ability to accomodate for all the needs of the people. However, following the Worlds Collide event, New Mobotropolis is no longer composed of nanites. Dr. Eggman's tampering with the very fabric of reality has drastically altered Mobius' history and one such result of this is that New Mobotropolis is now a regular city built from brick and mortar.