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By the glory of the Source, Castle Acorn! As it was in the days of our long-lost Mobotropolis!

–Maximilian Acorn upon arriving in New Mobotropolis, StH: #176

New Mobotropolis was a city constructed entirely of Nanites. Originally A.D.A.M.'s Nanite City, it was taken over and re-purposed by NICOLE, who reconfigured it into near-perfect recreation of the destroyed Mobotropolis. Located in Northamer, it was the capital of the Republic of Acorn and the home of the former citizens of Knothole.

New Mobotropolis


Creation of the Nanite City

The Nanite City

A.D.A.M., in a crazed desire to prove himself to 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, misinterpreting a statement by Dr. Eggman that he rationalized as being given the authority to do so. During the city's spread into the wilderness, it nearly 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. A.D.A.M. ultimately planned to use the Nanite City in order to gather Chaos Emeralds from across the galaxy. To this end, the location of the Nanite City was chosen for a specific reason; it was atop the long-buried Babylon Garden, which had a special warp-drive capable of opening "portals" through space. However, as it turned out, the Garden's systems were inactive as the two components of its ignition matrix were missing. A.D.A.M. was forced to develop an alternate plan that involved the creation of the Summoning Spire; however, this instead lead to the Great Harmony, and A.D.A.M. was destroyed. (StH: #152, #169, SU: #36)

Sometime after the destruction of A.D.A.M., NICOLE took control of the Nanite City and began reforming it to create a near-perfect recreation of 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 Eggman attempted to recapture all the prisoners taken during the bombing of Knothole, they were instead sent to the safe haven that Nicole introduced as New Mobotropolis. (StH: #175, #176)

Political Strife

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 therefore 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 Council of Acorn. (StH: #178, #179)

Attacks and Infiltrations

The citizens of New Mobotropolis rallying behind Princess Sally, ready to fight Enerjak.

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. (StH: #177, #180, #181, #182)

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. (StH: #185, #186, #192, #193)

New Mobotropolis during the Iron Dominion's takeover.

When Eggman was seemingly defeated, the Eggman Empire was taken over by the Iron Queen and Snively Robotnik. Heralding the Iron Dominion, they made several attempts against New Mobotropolis but were repeatedly thwarted, unable to subvert the city's shield. The Iron King launched an attack on the ruins of Robotropolis in an effort to cut off the city's power supply, but was thwarted when NICOLE relocated the power siphon while leaving the empty shell of the original in plain sight at Sonic's instruction. (StH: #203, #204, #206, #207)

However, after learning the full details of the city's nature, the Iron Queen launched another attack and, using her Magitek to take control of NICOLE, gained access to the city and quickly occupied it. Using NICOLE to control the millions of nanites, the city was reshaped to trap its citizens. However, several of the Freedom Fighters -- Sally, Sonic, Monkey Khan, and Tails -- escaped the city and, later, 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. (StH: #208, #209, #210, #211, #212)

This peace did not last, as the wizard Ixis Naugus soon arrived, claiming rightful ownership of the crown and causing more political conflict. Naugus used his magic to gain public favor, manipulating the people's fears of NICOLE stemming from her acts when controlled by the Iron Queen. Shortly after, Eggman launched the Death Egg Mark 2, which threatened to annihilate the entire city due to the use of its World Roboticizer. While Sonic and Sally infiltrated the Death Egg and disabled the device, though at the cost of Sally's Roboticization, it still posed a massive threat. Titan Metal Sonic was launched towards the city, as was the more subtle robot Tails Doll, destroying much of the Coliseum. Due to distress, NICOLE failed to repel the massive robot or even repair much of the damage it caused; Ixis Naugus used the opportunity to gain himself more support by defeating the robot and fending off further attack. Due to his actions, as well as his ability to magically crystallize and destroy nanites, the wizard gained more and more support and was able to take the crown for himself. The people began to demand NICOLE have less control over the city. (StH: #222, #223, #224, #225, 230, #231)

Near Destruction

The Battle Fortress fires upon the city.

While the shift in political power and the status of NICOLE causing conflict within, the city was soon faced with another threat in the form of the Battle Bird Armada. They had discovered that the long sought-for Babylon Garden was located directly beneath New Mobotropolis and planned to reach it by whatever means necessary. Ixis Naugus attempted to stop the approach of their Battle Fortress and failed; the people were evacuated beyond the city's walls as a distressed NICOLE created a "restoration point" for the city. The Armada disabled the city's protective shield, centered its airborne Fortress above Castle Acorn and fired a massive laser, destroying much of the surrounding area and burrowing deep underground. Babylon Garden later emerged from the hole but soon crashed into the nearby mountains, dragging the tethered Battle Fortress with it. Using the restoration point, the city began to slowly rebuild itself, though the large hole remained where the castle had been located. (SU: #35, #36)

With the Armada defeated, the Council of Acorn voted to exile NICOLE from the city to Freedom HQ. As a result, the nanites had to be manipulated through other means, and the crater remained where Castle Acorn had once stood. Rotor Walrus resigned from the Council in protest to the decision, and took up leadership of the newly formed Team Freedom-consisting of himself, Big the Cat, Cream the Rabbit, Heavy and Bomb-which served to protect the city. The new team proved itself quite capable, first in protecting the citizens from the collapse of a building caused by Tails Doll, and later in defending the city from another attack by the Death Egg. In the latter effort they were assisted by the newly formed Secret Freedom Fighters, who covertly struck at the invading Egg Swats and Team Metal. Naugus also took part in the latter battle, but due to mutations suffered from the Death Egg's activation found himself weakened and unable to participate for very long. Frustrated with having to share power with the Council of Acorn, he began making visits to the crater, under the pretense of investigating instabilities caused by the armada's attack. (StH: #235, #236, #240)

In reality, Naugus had used his magic to create a Ritual Chamber underneath Royal Military HQ, with plans to enslave the council using his magic and recreate his Order of Ixis. His plan was discovered by the Secret Freedom Fighters, who after observing both him and his apprentice Geoffrey launched an attack on their location. After a grueling battle, the Ritual Chamber was destroyed and the Freedom Fighters made their getaway, and Naugus was forced to claim that the disturbance had been the result of a cave-in and that he had saved the city. However, after Isabella Mongoose was elected to serve on the Council of Acorn, her first act was to call for a reversal of NICOLE's exile. The rest of the council-with the exception of an ailing Naugus-voted to allow NICOLE back under supervised conditions. (SU: #41, #42, #43, #44, StH: #241)

The city faced yet another catastrophe shortly after the restoration of Castle Acorn, which inexplicably began to collapse just as it was being opened. Making a connection with previous events, Team Freedom determined to lay a trap for the suspected culprit-Tails Doll-at the city's power plant. Their suspicions proved true, but the group faced an even greater challenge as Tails Doll commandeered a number of nanites in order to grow into a monstrous form that intended to destroy New Mobotropolis. However, the entire city was then engulfed along with the rest of the planet by the second Genesis Wave... (StH: #247)

In the irreversibly-altered timeline created by the subsequent Super Genesis Wave, the original Mobotropolis was still standing and under the Acorn rulership, rendering the new city nonexistent. (StH: #252)

Points of Interest

Castle Acorn

See: Castle Acorn

Civic Center

A social gathering center for everything between club meetings and city referendums.


Center of learning for Mobians of all ages. NICOLE was able to recreate the majority of the materials lost in the destruction of Robotropolis. Information is available in both book form and raw data.


Crops are produced within the city's walls-or from neighboring farms-and distributed here. Additionally, craftsmen that produce jewelry and other knick-knacks sell them here. (CSE)


The coliseum after the Iron Dominion's takeover

One of the largest buildings in New Mobotropolis, the Coliseum serves as the site for concerts and other such public events. This includes performances by the Forget Me Knots and the city's Dirt Hockey Tournament. It was also the site of the final battle between the Freedom Fighters and the Iron Dominion during the latter's occupation of the city. (StH: #201, #211, CSE)

King Frederick Airfield

Named after a former ruler of the Acorn monarchy, it is the main aviation hub for the city, capable of handling various types of aircraft. It features an underground hangar and two parallel runways, one of which features a launch ramp at one end.

Tommy Turtle Memorial Hospital

See also: Tommy Turtle Memorial Hospital

Named after fallen Freedom Fighter Tommy Turtle, it is the primary healthcare center for New Mobotropolis, offering patients the highest quality, most advanced healthcare available.

Science Center/Observatory

The main center for scientific research, this facility strives to keep the Republic of Acorn at the peak of scientific and technological advancement.


The New Mobotropolis Prison houses criminals being detained within the city. Its first inmates being Mammoth Mogul, Ixis Naugus, and the Destructix, who were teleported directly to the prison soon after being brought to the city along with the other inhabitants following being freed from the Egg Vineyard. It was also briefly home to Amadeus Prower, who was imprisoned for disturbing the peace during the events that led to the formation of the Council of Acorn. Mogul later orchestrated his own escape and that of his fellow villains through the use of the second incarnation of the Fearsome Foursome. They were followed by none other than Dr. Eggman himself, following his escape from the Iron Dominion and subsequent capture by Sonic and Tails. Following the city's fall to the Iron Dominion and then its subsequent reclamation by the Freedom Fighters, Eggman was released by Snively and the pair made their escape.

Outer Wall

This wall runs the entire length of New Mobotropolis' perimeter, and is equipped with powerful forcefield generators that serve as the city's primary means of defense against hostile attacks. It was able to repel the massed fire of the Egg Fleet, but was easily breached by Enerjak and later the Iron Queen. During the Iron Dominion's occupation of the city, this wall was transformed into a large dome that completely enclosed the city and entrapped those caught inside, but was returned to its original form when the city was liberated.

Chuck's Chili Dogs

See also: Uncle Chuck's Diner .

A popular five-star restaurant owned and operated by Sir Charles Hedgehog.

Royal Army HQ

The main military headquarters of the Republic of Acorn's military forces, with Geoffrey St. John's Royal Secret Service operating out of the top floor up until its dissolution. Following the destruction of Castle Acorn, it began serving as the meeting place of the Council of Acorn.

Julayla Memorial Garden

A public park near the Coliseum named after Sally Acorn's mentor Julayla, the garden allows inhabitants of New Mobotropolis a place to relax and unwind from the stress of daily life. The park also features a recreation of the Lake of Rings, which was shown to be able to generate Power Rings using nuclear fallout channeled from the ruins of Robotropolis. Like all the parks and forests in the city, it was created using nanites, but with an eye at eventually planting real trees and other plants. (StH: #204, CSE)

Secret HQ

See also: Secret HQ

A hidden bunker built beneath the city by NICOLE during the Iron Dominion occupation. It later became the base of operations for the Secret Freedom Fighters in their efforts to dethrone Ixis Naugus.

Mobotropolis School

The place of learning where the youth are taught school subjects in the pursuit for higher knowledge.

Power Plant

The source of the power that allows New Mobotropolis to function and be protected from outside threats, the power plant is a vital part of the city. It operates by using a power siphon positioned at the ruins of Robotropolis to drain the radioactive fallout from the destroyed city and refining it into clean, safe energy. This serves the dual purpose of powering the city while also working to eliminate a considerable environmental hazard. Unfortunately, this also made the power plant a target for Tails Doll, who attacked the facility in an effort to destroy its filters and allow the dangerous radioactivity into the city.


Background Information

  • The name of the city is taken from the original Mobotropolis, which, like many cities/states within the series, ends in -polis, meaning city.
  • The Dirt Hockey Tournament that takes place in the coliseum is undoubtedly a nod to Sonic and Tails' interest in the game in the Sonic the Hedgehog animated series.
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