A bulletproof door behind a Murphy door (hidden door) and a small hallway between which can be boobytrapped (gas, flamethrower, boiling water, gasoline, etc)
Awhile back I got ahold of a company who sells very secure and strong murphydoors. Best way to make a room like this is to create a new addition with double block construction with barbed wire/hazards in between, steel and rebar reinforcement with concrete inside, and regular side panels on the outside to be lowkey. Slanted sheet steel roof fitted with oil/grease. Underground is better for maximum strength.
I've seen people boobytrap a staircase by adding flamethrowers built into the rails which can be activated from the inside 🤣 Same guy used an AI tracking camera fitted to a BB gun as a deterrent and PA systems with audible warnings- out at the spot he was in the woods. Cool shit, haven't been able to find the video ever since 😂