Massive Ordnance Penetrator

The GBU-57A/B Massive Ordnance Penetrator (MOP) is a precision-guided, 30,000-pound (14,000 kg) "bunker buster" bomb used by the United States Air Force.This is substantially larger than the deepest penetrating bunker busters previously available, the 5,000-pound (2,300 kg) GBU-28 and GBU-37.

The Massive Ordnance Penetrator (MOP) is a weapon system designed to accomplish a difficult, complicated mission of reaching and destroying an adversary's weapons of mass destruction located in well-protected facilities.

[link to en.wikipedia.org (secure)]

I read in another thread but can’t find now there are military training exercises happening now in underground bunkers. I believe Utah was one place where they were doing but not sure.