I think a couple of Pharoahs built some cool bunkers a few years back. Hardly any valuables still left, ones that have valuables get taken by someone who’s not family, and in every case, the old fart is still in the bunker himself (at least his bones are). Lord Pacal was found at Palanque. Etc., etc., ad nauseum. People NEVER learn. Oh, and what happened to Howard Hughes? Is Ghenghis Khan still in his bunker?
Ditto Gates and company and their bunkers. Somebody built those things. The permits and plans are a matter of public record. In a "Book of Eli" scenario, it's just a matter of time before such "bunkers" will be breached.
If workers built them, then workers will know how to breach them.