Questions persist over the details of the construction, which some allege houses a massive underground military base and what appears to include huge underground cities, layered on top of each other 8 levels deep. It is 22 miles in diameter, and is capable of housing millions of people. What people? And why?

en.wikipedia.org...

The airfield is arranged in a pinwheel formation around the midfield terminal and concourses. This layout allows independent flow of aircraft to and from each runway without any queuing or overlap with other runways. Additional runways can be added as needed, up to a maximum of 12 runways. Denver currently has four north/south runways (35/17 Left and Right; 34/16 Left and Right) and two east/west runways (7/25 and 8/26).

DIA's sixth runway (16R/34L) is the longest commercial precision-instrument runway in North America with a length of 16,000 feet (4,877 m). Compared to other DIA runways, the extra 4,000-foot (1,200 m) length allows fully loaded jumbo jets to take off in Denver's mile-high altitude during summer months, thereby providing unrestricted global access for any airline using DIA. The sixth runway can also accommodate the Airbus A380.

The midfield concourses allow passengers to be screened in a central location efficiently and then transported via a rail system to three different passenger concourses. Unlike Hartsfield-Jackson Atlanta International Airport upon which the midfield design was based, Concourses B and C are not connected by any kind of walkway, they are only accessible via train.

The taxiways at Denver have been positioned so that each of the midfield concourses can expand significantly before reaching the taxiways. B Concourse, which is primarily used by United Airlines, is longer than the other two concourses, but all three concourses can be expanded as needed. Once this expansion is exhausted, space has been reserved for Concourses D and E.

All international flights requiring customs and immigration services currently fly into Concourse A. Currently eight gates are used for international flights. These north facing gates on Concourse A are equipped to divert incoming passengers to a hallway which connects to the upper level of the air bridge, and enters Customs and Immigration in the north side of the Main Terminal. These gates could also be easily modified to allow boarding on both the upper deck and the lower deck of larger planes such as the Airbus A380.

Once fully built out, DIA should be able to handle 110 million passengers per year, up from 32 million at its opening