If you want a tour of an Switzerland Underground Military Base made in the 70's, here ya go. It could house 180 soldiers for 6 months. If you need a reason for why disclosure of military action is taking so long, these places aren't easy to find and even harder to breach.
(www.youtube.com)
Cabal History
There are underground bases and railways connecting them, all over the world. The excavations are done by a massive 40-foot-wide borer, powered by a small reactor. It melts the drilled material into a glass-like compound, and lines the walls with it.
See this on Discovery? Sauce please.
This is only a short list of what can be found on this topic:
https://projectcamelot.org/underground_bases.html
https://ia904506.us.archive.org/18/items/UndergroundCitiesAndBases/200%20Underground%20Cities.pdf
https://amg-news.com/archives/6799
I think Munch meant the sauce on the boring machines.
It's in the links.