In Ground Safes (Floor Safes)
Although it takes some work installing a safe in concrete, it may be very worthwhile to do. By surrounding the safe in concrete you are accomplishing two things. It's hidden from view and also the volume of the concrete makes it a very tough safe to break into. Also, if a safe has a fire proof rating to begin with the concrete will only make the safe even more fire resistant!
General concrete floor Installation:
Break through the concrete floor with a either a sledge hammer or a electric hammer drill to approximate size. Dig to about 3 inches below position of safe. The more reinforced concrete that can be placed around safe, the greater the security. Partially fill hole with concrete mixture and reinforcement, place the safe in the hole, and push the safe down until the top is level with the finished floor. Finish adding the new concrete around the safe. Make sure the top of the safe is kept level with finished floor.