Cave 452 is an important location in Firewatch. Later on in the Cave 452, when you get the keys, you get locked by Ned Goodwin and you run to the exit of the cave. The next time you go there, and you have proper climbing gear, you discover Brian Goodwin's corpse, as he died because of a hiking accident. There is a broken climbing ropes set next to the corpse of him.
Cave 452 is located at the eastern end of Thunder Canyon. The main entryway is always open, but the majority of the cave requires a key to access.