The Radio Tower Cave (aka starting area cave) is a POI in Road To Eden, in the center of B-1 or north-east of the starting area.
The cave is 100% dark inside. Need 9v Batteries or Lightsticks to see something.
The cave is guarded inside by 2 skeletons, and divided in two rooms with several loot crates : Lockers, Flight Cases, Weapon Case, Ammo Boxes, Drawers, Desk, Book Shelves...
There is a little chance to find the Radio Tower Fence Key on a crate (see screenshot below).
Cave first part of the room.
Cave second part of the room.