[ilikeATMs]

Enthusiast safe tech here.

You cannot casually drill a safe. Not talking about your hardware store variety of safe, or a 'fireproof safe'. But a legit safe like you'd find in an ATM has a number of countermeasures to ensure that its not possible to drill the safe in a short amount of time.

Mixed into the steel is usually a number of drill-bit-breaking things like hardened ceramic/steel ball bearings, odd shaped chunks of metal, plastics which all react differently to different attacks in order to ensure that one attack does not compromise the door and that its near-impossible to do quickly. Bigger safes employ the use of fancy mixtures of concrete and metal to resist even more aggressive attacks like thermal lancing etc by turning the whole door/wall into a giant heat-sink.

Safes are really cool.

[PhantomGremlin]

I can understand how it's possible to design quite strong small safes. But what about big bank safes? Are the same design techniques used?

If not, why bother going through the front door? Isn't that door mostly for show? Aren't the other five sides mostly concrete and rebar? Isn't that easier to go through? Or do big safes really have thick steel on all six sides?

[ilikeATMs]

Depends on design and cost. Your thinking of a vault. Vaults have a solid door (as described above) and essentially its layers of security. The other 5 sides sometimes are the weakest point, but will still take significant amounts of time to penetrate on any properly designed vault.

No point in putting an extremely expensive vault door in a room that's got just concrete and re-bar.

The other thing is to make it harder to access those other walls as opposed to the front where you can walk up to it.