Book 2: Resistance Notes: Kebu Prison Camp

The prison camp of Kebu is built on the outskirts of North Chung Ling, an island in the eastern Fire Nation archipelago. It is a monitored encampment for 'enemies of the State' that for, whatever reason, the Fire Nation doesn't wish to kill outright. Some of the prisoners are press-ganged into military or work service elsewhere to support the growing war effort.

The prison is overseen by Uzon,the Warden and work overseer. Consider him to be like Colonel Link from Hogan's Heroes - invested in his prisoners but always scheming to advance. He's suspicious that prisoners are running an underground supply ring and network but can't prove it.

Notes of Chung Ling from the Avatar wiki:

 

The island hasn't quite industrialized yet to where we'll see it A:TLA (season 3, episode 7: The Runaway). There are some fledgling mining and industrial operations, but nothing substantial. The city is still seen as a seedy underbelly, but is under surveillance from the military guard of the nearby Kebu camp.

<Here's what the city looks like in the series. It wouldn't have the large Ozai statue in the center of the square, obviously...