All the bolts are on the inside. It's as secure as any welded safe.
Safes keep honest people honest, discourage amateur burglars, and protect the content from a fire. A home invader, if by some miracle he gets the drop on you will tell you to open the safe or he will blow your brains out.
That was my reasoning behind a safe room. In both meanings of the term. It's about the size of a big walk-in closet. All four walls are block and the door is a commercial grade steel security type with multipoint locking. The interior walls are currently unfinished because I plan to put up ballistic fiberglass insulation before closing in the walls. It's about 300 bucks for each 4x8 sheet. I had other expenses to deal with before plunking down the 4 grand I need for that. Silly things like doorknobs, kitchen cabinets and faucets.
I'm not a fan of bunkers, but in some situations it's a good thing. My main thought was my wife had a safe room if I were not there. Nobody is getting in that room without heavy artillery or explosives. The other reason was it eliminated my dislike of safes, which among other things is like a neon sign that says "expensive shit inside". My room is barely noticeable. My final act is a sliding bookcase to conceal the door.