I watched a generic Da-Vinci-Code-like french movie that, in a certain point, featured a secret society trying to find an item of great value that was lost in a vault built centuries ago (millenia, if I remember it correctly). Obviously, to gain access to the vault, a key is needed - since it's the only way to open it.
In this type of narrative, I think that the difficulty in opening the given door, vault, chest or whatever is not in the actual "opening" of the device, but in the process of locating it. All that "it was lost in time" thing is a good explanation as to why no one has opened it before - because no one could find it - 'cause if you think about it, if anyone knew where the vault was located, they could've just blasted their way in without the need for some big search for the goddamn key.
As a narrative element, I'm all for it. But in the real world, people would blow shit up.
The Actual Question
Suppose this vault exists and a certain group finds it.
From an engineering point of view, would it be possible for an ancient civilization to build a contraption capable of enduring modern day attempts to break in?
If yes, I would like to know what would this device be like and why dynamite, drills and general modern-day brute force should be useless against it.