Metropolis (メトロポリス,Metoroporisu?) is a location in Sonic Chronicles: The Dark Brotherhood. The game actually starts with the destruction of Eggman's Metropolis. GUN attacks the city in full military force, while Sonic, Tails, Knuckles and Amy battle the Doctor on board his latest Egg Carrier (which bears closest resemblance to the Egg Stingray from the end of Sonic Heroes). Tails succeeds in sabotaging the Carrier, such that the airship disintegrates and crashes into Metropolis, devastating the city in a massive explosion as the GUN forces and the heroes retreat.
Following this defeat and with Eggman missing and presumed dead, the ruins of Metropolis were left to rust. The only visitors were those human scavengers brave or foolhardy enough to raid the ghost city for salvageable metals and technology, until more guests began to arrive.
The black-clan named the "Marauders" secretively moved into the ruins of Metropolis, using the devastated city as their main base of operations on Sonic's world. The Marauders hacked into obsolete Eggman robots, deploying them to guard their operations while Procurator Shade moved forwards with the plan to capture the Chaos Emeralds. Using the Emeralds, the Marauders were able to move Angel Island from above the Mystic Ruins to Metropolis.
In Chapter 5, Eggman provisioned Sonic with the necessary information to infiltrate the Metropolis Underground and stop the Marauders. The hedgehog arrived seconds too late, though; after expropriating the Master Emerald from its plinth, the Marauders abandoned the stronghold and returned to the Twilight Cage—leaving Knuckles's floating continent to crash square into the city.
↑Later in The Dark Brotherhood, the team learns that Robotnik was in fact saved and nursed back to health by one of his medical robots; he is eventually discovered, slowly rebuilding his power base from a secret underground facility in Green Hill Zone.
↑As alleged by the adviser for the tower escalator puzzle, Sonic Chronicles: The Dark Brotherhood, Chapter 5