AnScAggie said:
Easiest is to camouflage it with a hidden door. Otherwise you'll be doing a large retrofit to strengthen the walls and give you a way to hang a safe type door or heavy steel door. Also having a safe door won't do any good unless you strengthen the walls because it's easy to knock a hole in the wall with studs on 16" centers.
Yep, security though obscurity.
I've seen a coat closet converted like this. Basically cut the door down a bit, add a deadbolt and framed in the bottom 6" of the door way. Then mounted a custom built halltree on 2 Heavy duty sliders. They added a separate small bench in front and it looks like a halltree and bench on the wall, would never guess its hiding anything behind it unless you walk around to account for the missing couple of sqft.
Halltree slides open and then there is a locking door behind it.
Serves as a great bench to put shoes on/off and still gave a place to hang coats and such.