Has anyone heard about the deep underground military bases in america and britain?

I have heard they are used as research facilities and weapons and equipment stores. They can also be used to live in, should a disaster occur. I have seen a picture of the drilling equipment on line. The drill heats the rock up to an extreme temperature and melts it's way through. 7 miles can be completed in a day. There is an underground base in dulce, one below denver airport and there is one in the brecon beacons in wales england. Do any people know of bases or know of any near them? And what do people think of these bases? Should all this secrecy be kept from us when we are funding these facilities? Is an agenda going on here?