I have a secure gun room. Took a third of my basement and built a reinforced wall with a safe door. Wish I had used half the basement. Took a lot of advise from John Mann about building it. Put up a chain link fence over head before putting in a drop ceiling. Outside air venting for fresh air. Dehumidifiers for moister control.
Built wall racks that hold guns upright. They work great, but you can not see most of the guns at all. So I am thinking about building one wall with horizontal racks for displaying guns so I can see them better. If I like it, I will do two more walls, even if it means I need to thin the herd. Like many here I am almost too old to keep buying more and might as we’ll reduce the total number of guns and at the same time upgrade in a few areas.