I’ve heard those lines way too often. You cannot build in a way that guarantees safety for every scenario. Your concrete fails, water erodes into the caverns, earthquakes, volcanos, or simply someone digging in that spot. How the hell do you believe we can build something that pasts for longer than mankind has documented it self in any way? The Nazis failed to build something that would last a thousand years, that is a fraction of the time you claim will be absolutely safe