If the area is hard to get to, consider a modular safe, like the Zanotti, that can be built in place. Not as heavy as some, and not fire resistant, but adequate for most folks.

A while back, someone said that he was building a gun room and planned to use nothing less than 3" face hardened armor plate for the walls and a bank vault door because that was the minimum anyone should have. I, being ye olde picker of nits, asked him if he had any idea how much sheets of 3" armor cost and how much they would weigh. Never got an answer.

I guess life is about compromises.

Jim