Here are 15 images and three quotes showing what Hell is. Hell is the place where the teens went camping and stayed during the invasion.
These images I got from google, and I choose these ones because this is what I vision what Hell would look like based on the character's description.
The quotes are form the novel describing Hell
Quote 1:“quiet, shady, cool, and damp”
Quote 2: “No place was Hell, no place could be Hell. It's the people calling it Hell, that's the only thing that made it so”
Quote 3: “it's a nice creek”