If you have the space you have the ultimate safe room as well as gun vault. If you are going to have it do double duty, make sure you have a sufficient but hidden HVAC/water/sanitation system. My wife thinks I am a little out there, but I am installing (almost finished) a survival bunker. It is built into a hillside, has a garage that will eventually shelter 6 large vehicles and a few ATVs. Started with a natural cave that has expanded into 8,000 square feet (not counting garage) and has solar panels, a windmill, and on the property are 3 natural springs that we have 2 prebuilt hydro dams that will install in a couple of hours each. No windows but I see that as a plus. Since we own the 80 acres around the place we feel somewhat secure and now go there on weekends for the finishing off projects. I am relying on mostly not being found for security, but if we are found by hostile folks, they may regret that finding. I bought an old tug boat for the fuel tanks and generators, 2 5,000 gal tanks and a 20kw and a 7 kw generator. All nicely unfindable. We can run the place on just one set of solar panels, or one hydro/electric unit without disrupting the natural environment. As it is primarily an old cave it is a constant 65% year round, and we will not have to expend juice to heat or cool it. Got a septic system that would service a small subdivision. And a natural small lake up hill of us that refills with rainwater, snow runoff all the time. It drains into a 3,000 gal tank that provides gravity water pressure. And to think my wife told me I was nutz to buy the place for a song 25 years ago. Have spent about 90K fixing it up, including all interior fixtures, doors, 6 bedrooms w/3/4 quarter baths, 2 great rooms, and an office and a conference room that will double as a dorm if we come across non family that we want to help(unlikely).
Yeah I am a little paranoid. The galley is of absoutely full service commercial type (from a wrecked Great Lakes ship), and we have a large safe room/armory, not that I think we will need as the ony exterior door was built from the remains of an old armored car, and entry via the garage is likewise protected. Each vehicle stall is separated with a really tough door to finally get to the house entrance which is going to have a drop down door that will stop .50 caliber, thinking of upgrading it to 20mm.
It actually a nice place to bring the whole family on weekends even if it is a little drive, but the grandkids can play in the woods and practice survival techniques, they think it is great fun. We are teaching them to relate to the wildlife without telling they might have to eat it some day.
Yes, I am having a good time planning for survival with out machinegun nests, and only a couple of spider holes.