The Iron Fortress is a royal palatial iron citadel located in the Dragon Kingdom from which the Iron Queen and the Iron King sought to establish as their own palace and the namesake capital of the powerful Iron Dominion, to dominate all of the Dragon Kingdom and soon all of the peaceful planet of Mobius.
The Iron Fortress included an armory housing many captured weapons, including the Fan of Fen Xing within its mighty meter-thick armored walls and it has 2 heavily reinforced doorways that can be only opened from the inside.
The evil duo were forced from this location by Sonic the Hedgehog, Miles "Tails" Prower, and their nemesis Monkey Khan after they infiltrated the fortress and used the fan to defeat the two.
The pair later reclaimed their castle fortress sometime before the Iron Dominion's taking possession of New Megaopolis.
After their departure from the Dragon Kingdom, it became a base for the Raiju Clan as they enforced the Dominion's will. It was then stormed by the allied forces of its 3 former invaders, Sally Acorn, and the Destructix under Fiona Fox, leading to a pitched battle that ended with the Raiju Clan forsaking its loyalty to the Dominion and claiming the fortress as its own.