Under Stalag 13 are placed several underground tunnels. These tunnels have been created by the prisoner through the removal of tons of dirt from under the camp. The tunnels are located throughout the camp, where they lead to such places as the barracks, Klink's office and the cooler, or outside of the camp via the tree tunnel entrance. Inside the tunnels is a radio room where the radio which the prisoners use to stay in touch with London is hidden, a weapons locker for weapons and a clothing locker which contains the costumes that the prisoners would wear as disguises for certain dangerous missions. Also under the tunnels is Carter's lab, where he would conduct his experiments to create explosives for missions. There are also areas inside the tunnels where those who are being helped to escape Germany would be kept until a way is found to help get them to the next point on their journey.