Robotropolis, formerly Mobotropolis, is the capital of the Robotropolis Zone and formerly the Kingdom of Acorn.
The city was renamed to celebrate Robotnik's victory over his enemies, as the Acorns were the last power to fall. The once medieval city has been almost entirely rebuilt into a sprawling industrial wasteland, and it is not uncommon for people to be crammed into tenements that are placed right next to massive industrial districts.
Even during the day, the city can be rather dark due to the sheer amount of pollution overhead.
It is frequently the target of raids by the Mobotropolis Freedom Fighters.