Google HIDDEN ROOMS and see all the clever ideas… Usually under stairs, or behind rotating bookcases…
If you have an extra large room…..consider adding an extra wall… (minimal expense!) with a rotating bookcase, or secret door panel, and call this your safe room. If someone breaks into the front door, you could roll out of bed, and go thru your rotating bookcase, and be safe…
you’d have a place to go…instead of having a gun battle…sit in there, and call the cops from a safe location..add a separate door to the outside, and escape the entire house if you want….it is just fun to think of these things…
Sure you’d probably NEVER use it….but it is kinda nice to have it….like getting insurance… it’s there.
Or reinforce it a bit, and call it your tornado/ storm room.
Or a place to store your valuables…if you rent your house out on Air BnB…
The thing is… when you design a house….add this flex room now while it is cheap to do, and let the future determine what it will become….maybe it will be a place for your cat to have kitties….whatever…
But is is an example of getting something really interesting for nearly free, that would be very expensive later on.