A.D.A.M. in his desire to be loved by his father Dr. Eggman, started to rebel against him. During his plan to rise above, A.D.A.M. used the Nanites to create a growing city that would soon engulf Mobius, thanks to a statement by Dr. Eggman that he rationalized as being given the authority to do so. During the city's spread in the wilderness, it engulfed Lupe and her Wolf Pack as they were traveling through the area. Thanks to the efforts of the Knothole Freedom Fighters, the city's expansion was stopped and the Wolf Pack was able to escape without any apparent harm done to them. The city then played a crucial role in the Great Harmony as the focusing point for which every Chaos Emerald in the galaxy was gathered at the Summoning Spire with the exception of the Master Emerald, and also became the site where Tommy Turtle sacrificed himself to the Egg Fleet's cannon-fire in order to destroy A.D.A.M. once and for all. Sometime after the destruction of A.D.A.M., NICOLE took control of the Nanite City and began using the Nanites to create a picture perfect recreation of Mobotropolis that she called New Mobotropolis, intending to surprise her friends. However, due to the destruction of Knothole by the Eggman Empire, she was forced to unveil her side-project to her friends early; when she and Tails rewrote the transit location of the Egg Beater's teleportation beams, nobody transported to the Egg Grapes, but to the safety of New Mobotropolis instead.
Following the rescue of the citizens of Knothole from the Egg Grape Chambers, a number of enemies of Sonic the Hedgehog and the Freedom Fighters found themselves transported to New Mobotropolis as well, including Mammoth Mogul, Ixis Naugus, Nack the Weasel, Bean the Dynamite and Bark the Polar Bear. Mogul quickly attempted to rally the people to his leadership, but he and the others were teleported to New Mobotropolis' prison cells by NICOLE. They later escaped after Mogul forced Sonic, Mighty the Armadillo, Mina Mongoose, and Miles Prower to serve as his new Fearsome Foursome, allowing him to obtain the Chaos Emerald stored at Castle Acorn and escape from prison with his fellow criminals. Most recently, the New Mobotropolis prison has received another occupant, none other than Dr. Eggman himself. Eggman had escaped from the Iron Dominion and was discovered and captured by Sonic and Tails. Unfortunately, he was later freed by Snively after the Dominion occupation of the city was defeated. The Iron Queen herself was arrested in the city, but moved to the Dragon Kingdom for further incarceration.
Shortly after relocating to New Mobotropolis, Amadeus Prower and several others staged a protest intent on removing the Acorns from power due to their failures in the past. Amadeus was subsequently imprisoned for his role in what was seen as a treasonous riot. He later explained to King Elias that under the rule of the Acorns they'd lost both Knothole and Mobotropolis, while a group of children had made the most progress in protecting the people. He thusly believed that the people should have the right to choose their own government rather than be stuck with a failing monarchy. Rosemary Prower and Tails would later break Amadeus out of prison resulting in a fight between Sonic and Tails while Amadeus confronted King Elias. While Sonic and Tails made amends, Sally was forced to intervene when she was alerted to the situation by NICOLE. She berated the two for going directly to fighting and told them of her own experiences when she headed the Knothole Council and asked them to find a compromise, resulting in the creation of the seven-member Acorn Council.
Dr. Eggman immediately launched an attack on New Mobotropolis after learning that the inhabitants of Knothole had been transported there. Claiming the city as his own by virtue of the nanites that had constructed it, he attempted to break in first by bombarding it with the Egg Fleet, then later by using his Egg Beater exo-suit. Both these attempts were thwarted: the first by the city's energy shield, and the second by the combined efforts of the Knothole Freedom Fighters and Chaotix. He later attempted a second assault using his Egg Nautilus, but was halted by Sonic with news of the impending threat of the new Enerjak. Enerjak soon arrived in New Mobotropolis in person, and revealed himself to be Knuckles the Echidna, brainwashed by Dr. Finitevus. New Mobotropolis was then damaged as Enerjak was confronted by first Sonic, and then Shadow the Hedgehog. The resulting energy drain required to repair the city forced NICOLE to lower the shield, allowing the arriving Egg Fleet to capture Enerjak.
Later, Sonic himself would infiltrate New Mobotropolis-specifically Castle Acorn-in order to steal a Chaos Emerald for Mammoth Mogul, on the condition that he would release Tails, Mighty, and Mina from his control. Scourge the Hedgehog also infiltrated the city in hopes of attacking Sonic, and Anti Tails of the Suppression Squad was dispatched to New Mobotropolis on a bombing mission that he used as cover for a meeting with the Freedom Fighters.
Another hostile incursion against New Mobotropolis came when the Iron Queen and Snively Robotnik arrived over the city. The Iron Queen used her Magitek powers to possess Bunnie D'Coolette and Monkey Khan's cybernetics and forced them to attack the city's inhabitants. It was only through quick action of the Knothole Freedom Fighters and Chaotix that serious harm to the city and those living there was averted and the two possessed were restored. The Iron Dominion would attempt another assault on the city as they persued members of the Freedom Fighters whom had taken custody of a delusional Dr. Eggman after he had escaped from the Eggdome. The Freedom Fighers retreated to the safety of the city, the shields managing to repel them this time, even withstanding repeated blows of the Iron King's Tremor Mace, the attackers being forced to retreat, suffering their first real defeat against the Republic of Acorn.
After finding out that being technological in nature NICOLE and New Mobotropolis can be easily controlled by the Iron Queen's Magitek, the Iron Dominion once again invaded the city. When NICOLE warned them to leave the Iron Queen took control of her, allowing her forces to flood the city and occupy it. However, several of the Freedom Fighters-Sally, Sonic, Monkey Khan, and Tails-escaped the city and managed to free NICOLE from the Iron Queen's control. NICOLE then assisted a small group of resistance fighters in their efforts against the Dominion, and this group joined NICOLE and Sally's team in defeating the Iron Dominion and driving them from the city. A week after the Dominion's fall, the city had returned to its previous peaceful condition.
King Ixis Naugus
Former King Maximillian Acorn
Former Queen Alicia Acorn
Princess Sally Acorn
Geoffrey St. John
Sonic the Hedgehog
Big the Cat
Vanilla the Rabbit
Cream the Rabbit
Cheese the Chao
The Council of Acorn
The Team Freedom
King Elias Acorn
Knuckles the Echidna
Espio the Chameleon
Mighty the Armadillo
Vector the Crocodile
Ray the Squirrel
The seat of the monarchy and the crown jewel of New Mobotropolis. Built in memory of the splendor of Old Mobotropolis, Castle Acorn is home to the royal Acorn family. Since the revolution it also acts as the primary meeting place for the Acorn Council. The counselors all have their offices and optional residences within Castle Acorn.
A center of learning for young and old alike. Nicole managed to recreate almost all of the material lost to the Robotropolis disaster. The information is both in raw data and in books.
The social gathering hub for the citizens. Everything from small club meetings to full-city referendums can be held in the beautiful facility.
Ever self-sufficient, the Mobians tend to their crops within the city's protective walls and distribute their goods here. Craftsmen are out in force as well as selling clothes, jewelry and knick-knacks of all kinds.
The single greatest place to eat in all of New Mobotropolis is Uncle Chuck's. When he's not researching in the Science Center, Sonic's uncle is making the best batch of chili-dogs ever. The casual atmosphere and friendly faces make it the most popular place in town.
Inside the Diner
While the Freedom Fighters protect everyone, it's up to the Royal Army to provide elite protection for the Acorn family and members of the Acorn Council. The facilities have everything the Royal Army needs to train and maintain the best of the best. The top floors are reserved for the Secret Operations branch headed by Commander Geoffrey St. Johns.
To survive in the world of Dr. Eggman and the United Federation, New Mobotropolis has begun cutting-edge scientific research in their new Science Center. All the disciplines are welcome here - not to mention any open and curious minds.
Every day the youth of New Mobotropolis enter into the halls of learning. Bright young minds are inspired and encouraged to question and explore the boundless academia.
All the nanites that make up New Mobotropolis require a lot of power. An underground conduit runs all the way to the radioactive remains of Robotropolis and siphons off the dangerous energies. These are purified in the Power Plant and used to give clean energy to the city and its citizens while cleaning up a bad mark on Mobius.
Named after a previous King Acorn, the airfield is the primary launch site for all of the Freedom Fighters' aircraft. Everything from the Tornado to the Freedom Fighter Special mk. II takes off from here.
The best medical facilities in the world can be found in New Mobotropolis. Dr. Horatio Quack oversees the hospital on all levels as the staff tends to everything from a runny nose to serious ailments. The maternity ward welcomes the newest citizens with the best care one could hope for. The facilities are named in remembrance of a fallen Freedom Fighter who ensured the well-being of everyone.
When the Freedom Fighters caputre criminals, they are taken to the Detention Center. They are kept in highly-guarded cells. Should one of the criminals try to escape, NICOLE has installed teleporters to take them back to the Detention Center.