Green Hell: also the nickname for Germany’s most famous automobile/vehicle race course. (Nurburgring).
Been there twice.
Green Hell was the name for the Jungle Operations Training Branch which used to be the area between Ft Sherman and the Chagres River. Some of the densest triple canopy rain forest in the world. Every soldier who deployed to the tropics had to do the “course” there for decades. They used to have an interesting Zoo so the soldiers could see what they may encounter in the wild. Jaguars, crocodiles, they even had a 28 foot Anaconda (even though they aren’t native, it had escaped from a plane crash, IIRC). We used to take the kids to the “Zoo”. Fun times.