Here's an overview of the basics. According to the conspiracy theorists, Denver already had a fine airport, Stapleton International. But despite widespread protests, Denver International was built and opened in 1995, with fewer runways, thus reducing Denver's capacity. Its construction began with five mysterious buildings that were completed and then buried intact, with the cover story that they were "built wrong". Up to 8 levels of underground facilities are said to exist, and workers who go there refuse to answer questions about what they do. The entire airport is surrounded by a barbed wire guard fence, with the barbed wire angled inward, to keep people in, like a giant prison, not out like at other airports. And if viewed from the air, the runways are revealed to be laid out in the shape of a Nazi swastika.
Questions about what the government might be doing in this underground base may have been answered in 2007, when fourteen commercial aircraft reported spontaneously shattered windshields as the presumed result of electromagnetic pulses.
Indoors, the airport gets even stranger. The Illuminati appear to have detailed their plans for global genocide and a New World Order in two large murals. The first depicts a huge Nazi soldier with dead women and children scattered around him, and the second shows Third World populations dying, a few elite species protected from the apocalypse in sealed containers, and the Mayan symbol for 2012 presiding over all. In the floor near the murals is written "Au Ag", the abbreviation for the deadly toxin Australia Antigen, evidently the Illuminati's weapon of choice to accomplish the genocide.