From an internet source:
There is the Deep Underground Military Base underneath Denver International Airport, which is over 22 miles in diameter and goes down over 8 levels. It’s no coincidence that the CIA is relocating the headquarters of its domestic division, which is responsible for operations in the United States, from the CIA’s Langley headquarters to Denver…DIA serves as a cover for the vast underground facilities that were built there. There are reports of electronic/magnetic vibrations which make some people sick and cause headaches in others. There are acres of fenced-in areas which have barbed wire pointing into the area as if to keep things in, and small concrete stacks that resemble mini-cooling towers rise out of the acres of nowhere to apparently vent underground levels. The underground facility is 88.3 square mile deep. Basically this Underground Base is 8 cities on top of each other! These city-sized bases can hold millions and millions of people, whether they are mind controlled, enslaved NWO World Army Soldiers or innocent and enslaved surface dwellers from the towns and cities of America and Canada.