Pukchang Concentration Camp
The Pukchang camp (Camp 18) is around 28 square miles in area. It was established in 1958 but according to reports the camp stopped operating in 2006.
The capacity of the camp was about 30,000 prisoners.
The camp used to be for politically unreliable people and it exploited prisoners with hard and dangerous labor in coal mines and various factories (such as brick, cement and glass factories).
Although following satellite images show little change in the area, it seems that the camp is still partially functioning.
In the images you can see various factory facilities, mines, barracks for the prisoners as well as offices and housing for the guards.