Robotropolis

Robotropolis was the capital city of Dr. Ivo Robotnik's global empire. It formerly existed as Mobotropolis, but was transformed into a desolate, mass polluting, technological city. When a new version of Robotnik currently known as Dr. Eggman came to this reality, he too used the city as his capital, until it was destroyed by a nuclear strike by Station Square.

Becoming Robotropolis
Robotropolis was formerly the city of Mobotropolis - capital city of the Kingdom of Acorn and the first ever multicultural city since the birth of Mobians. Five years after the Great War ended, the kingdom's chief scientist, Julian Kintobor, took over the city using his robotic hordes of SWATbots. The majority of the city's population was captured and roboticized, though some managed to escape to the sanctuary of Knothole in the Great Forest, including the members of the Original Freedom Fighters, King Maximillian Acorn's daughter Sally and a few other children which went on to become the Knothole Freedom Fighters. (StH: #50, #71, #142, #143)

Restoration and Retaking
After numerous engagements against the Knothole Freedom Fighters, Robotnik was eventually killed by his own weapon, the Ultimate Annihilator (due to tampering from his nephew Snively). The Mobians then retook the city and began the tedious task of restoring the city to its former glory. However, the arrival of an alternate universe version of Robotnik (now calling himself Dr. Eggman) spelled disaster for Mobotropolis. Dr. Eggman was able to retake the city with relative ease, distracting the Freedom Fighters by leading them to his satellites in orbit, while launching hordes of Shadowbots to reclaim the city. When the Mobians fled to Knothole, Eggman rechristened the city Robotropolis. (StH: #50, #51, #75, #76, SSS: #2)

Destruction
Robotropolis was later destroyed in a nuclear strike by Station Square. The harmful fallout is currently kept within the former site of the city by a shield originally designed to protect the city. When the Bem pitted Eggman and against Mecha Sonic and Mecha Tails, a holographic recreation of Robotropolis became their battleground. (StH: #110, #118)