Big MT

The Big Empty is a high-tech location located east of the Sierra Madre.

Background
A pre-War military facility, the Big Empty has remained secure ever since the Great War, its scientific secrets and treasures undisturbed, protected by robotic guardians. The installation has several medical research centers.

Its security was breached sometime in the 23rd century by Elder Elijah, who barely made it out alive with a supply of high-tech slave collars and a captive Brotherhood scribe.

Appearances
Big Empty did not appear in any of the published games, but was to appear in the canceled Fallout 3 project by Black Isle codenamed Van Buren, as the Big Mt. Training Facility), an old military boot camp that after the Great War is being run by Mr. Handy robots . It is also mentioned in Fallout: New Vegas add-on Dead Money.

Behind the scenes
At some point during the development of Van Buren, Big Empty was merged with the Leavenworth prison into what became the Tibbets Prison, which was still referred to as "Big Empty" by some of the developers. It is currently unknown whether the mention of of Big Empty in Dead Money refers to the pre-merge version of this location, or to Tibbets.