Trying my hand at world space creation with the CK, this is where I am at so far. A basement living area under Red Rocket gas station, the trap door is located in the back office of the place. Inside you will find a regular settlement workbench (Not the crappy interiors one like in the home plate player home.) As well as a custom power pylon that generates 5000 units of power and radiates it off with a radius of 5000. Currently there is a lighting issue, when you enter the basement it will be dark, simply  go into build mode and pick up, then put down the lone light bulb in the center of the rooms ceiling. The floor too is still movable, currently working on a fix; so dont pick it up or you will fall into the abyss. Anyways, enjoy.