Djorn Major XJ-003
Djorn Major XJ-003 was a maximum security penal facility in use by the United Federation of Planets. Originally intended to house only the most violent of criminals, during the Federation Civil War, Admiral Doenitz converted the facility into a Political Prison.
There, he kept the majority of his political enemies, as well as captured members of the 52nd Fleet while they awaited execution.
Against Orders members of the crew of the USS Nimitz conducted a rescue operation against the facility and rescued Tagon. During the raid the facility was badly damaged, forcing it to be shut down.
After the Federation Civil War, the facility was repaired and reopened, and once again resumed it's operations as a maximum security facility.