Agreed. With all the mining equipment coupled with tunneling for rail systems, sewage/drain systems et al, there exists an enormous capability for construction of deep underground facilities. I have no doubt it's been done.  We do hear specks of info once in awhile, too.  This equipment doesn't sit around much.  We've all seen video of those giant tunneling moles, some as big as 100' in diameter, churning through the earth. How about Musk's Boring Company and its' potential. He got up and running real quick.  Where'd he get that equipment from? Someone's making them. Oh, yeah, there's stuff down there.