Cheyenne Mountain Cheyenne Mountain is a location in " " , which can be reached from Bunker Epsilon . Background . During the 20th century , the American military created a facility underneath Cheyenne Mountain , one mountain in a range of many on the western side of the United States . These ranges extended from Canada , far to the north past the United States border , down into the southeast of the country . Vault 0 is located here , housing the Calculator . Background . NORAD . Before the Great War , Cheyenne Mountain Operations Center was host to four commands : North American Aerospace Defense Command ( NORAD ) , United States Northern Command ( USNORTHCOM ) , United States Strategic Command ( USSACCOM ) , and Air Force Space Command ( AFSPC ) . Throughout the Cold War , Cheyenne Mountain was considered a primary target in all first - strike and second - strike scenarios . Although the mountain was designed to withstand multiple direct hits from nuclear weapons , projections were universally pessimistic as to the survival of the installation . Vault 0 . Vault 0 ( Vault Zero ) , unlike most Vault s involved in the Vault Experiment , was not an experiment in human behavior . It was constructed by expanding and reinforcing the Cheyenne Mountain Complex in Colorado and was by far the largest of the underground Vaults ( by volume ) . Many of the areas that comprise the massive interior layout of Vault 0 were originally designed to be the size of ( and were often compared to ) aircraft hangars , warehouses and factories ; these zones were for the construction of various machines that were ostensibly designed to serve the Vault Dwellers . A massive amount of war robots and a cybernetic computer to control them ( and serve as the Vault ' s overseer ) were placed here to ensure humanity ' s rebirth after nuclear war . However , the Calculator becomes corrupted , drives the population of the Vault to extinction , and initiates the pacification protocol , originally intended to kill all of the possible enemies to the people of Vault 0 . A massive army of robots emerges , producing more and more every day using several pre - war manufacturing centers such as Great Bend and Canyon City . The internal power supply of Vault 0 was not enough however and the Calculator had to use the nuclear reactors of Buena Vista to help power its growing robot war machine . Soon the Calculator became the main enemy of the Brotherhood of Steel . The Warrior , hero and general of the Brotherhood , led his squad to confront the Calculator , defeating the robots , which guards their main base . " Plutonius , " a nuclear warhead from Kansas City , was placed on the nuke carrier , brought closer to the Vault entrance and eventually blew up the entrance . The Warrior and his squad managed to survive the explosion thanks to a nearby fallout shelter ( a small military bunker ) . Soon , the final battle begins . Crater . By 2253 , a huge section of the mountains became a great radioactive smoking crater , giving birth to a large population of glowing ghouls . Coupled with attacks on Denver and the Rocky Mountain Arsenal , Boulder became the center of a triangle of hellish death . Mission . The mission at Cheyenne Mountain requires the player to transport a nuclear warhead to the door of Vault 0 and then to get to safety in a bunker nearby . Notes . Although Cheyenne Mountain isn ' t mentioned in " Fallout 2 " , NORAD is . Listed as a footnote , buried in the network script of the Gecko Power Plant computer terminal . NORAD is listed as " offline . " Appearances . Cheyenne Mountain appears only in " " .