Capital City Prison

A The Capital City Prison or Prison Tower is a large, fortified stone tower located in the Fire Nation, inside the hollow volcanic crater that forms the imperial capital. Highly prioritized criminals are kept here, although it is unknown whether this prison or the Boiling Rock holds more infamy. Iroh was one of the few prisoners being held within the penitentiary, until he managed to break himself out. Some Kyoshi Warriors were imprisoned here also.

After the failed Invasion on the Day of Black Sun, the prison was used to house many of the captured invaders and war prisoners, like Bato, until their move to the Boiling Rock. After Fire Lord Ozai was defeated by Aang, he was incarcerated here.

The interior consists of various cells made of stone with cages, which are watched over by guards like Ming. This design allows guards to enter without being attacked (it should also be noted that even though the prisoner is locked in the cage, the actual cell door is generally left unlocked).

Trivia

 * Some of banished Fire Nation Royal Family is stayed here, if imprisoned. Like banished Phoenix King Ozai, and banished General Iroh.
 * The prisoners will be get stressed, by nobody who can talk, except the warden and visitors.
 * The prisoners is actually had little strange, just like they didn't get out walk from their cage, because it's unlocked!