My post divorce gun room is much smaller than the pre divorce one was. The pre room was like yours, built in the basement. The access door was to the left of my work shop work bench and was covered by a framed sheet of pegboard complete with hanging tools. You pulled open the hinged peg board to reveal the actual gun room door. Inside was a window less area with horizontal wooden glass front rifle cabinets on the wall with wooden bookcases below for short gun display.
Now my post divorce room is a tiny little thing about 3 times the size of a walk in shower. Someday I will have the larger room again. At least I got to keep all of the contents.