Big MT

The Big Mt. Research and Development Center,referred to as the Big Empty after the Great War due to letters "M" and "T" present on doors and no mountain left, is a high-tech military research facility in the Mojave Wasteland. Many of the Mojave's mutated creatures originate from here.

Background
A pre-War military operation, the Big Mountain Research and Development Center has remained secure ever since the Great War, its scientific secrets and treasures undisturbed, protected by robotic guardians and well-concealed by its sheer size. Originally the Big Empty was inside a mountain, however during the Great War the mountain was destroyed, leaving a huge crater.

Nowadays, the installation is described by Elijah as a "treasure box" and "a scientific graveyard of Old World misery". The facility houses several pre-War scientists, their personalities preserved by Think Tanks. There, they perform experiments that can only be described as atrocities on anyone unlucky enough to find themselves at the facility. People subjected to them are often damaged beyond recognition by the procedures - some could only hear static, others became gibbering wrecks. Other technologies found at the Big Empty include holorifles, Saturnite alloy, hibernation chambers, Securitrons, the hazmat suits worn by the ghost people, and the vending machines found in the Sierra Madre. The Big Empty is also known to contain holograms, though only N.E. was able to perfect the technology, selling it exclusively to Frederick Sinclair, so the holograms of the Big Empty are far less lethal than those of the Sierra Madre.

Christine Royce, a Brotherhood of Steel Knight, came across the Big Empty in her hunt for Father Elijah. When she finally found him, he trapped her in one of the medical research labs, modifying her brain with cybernetic enhancements to the point where she can only think and dream in numbers, but also causing irreparable damage to her brain. He then left to search for the Sierra Madre, taking with him a supply of explosive collars and a holorifle. Not long after, Christine was freed by a mysterious courier, Ulysses, who encouraged her to continue her hunt.

In 2281, the Courier arrives at the Big Empty, where they will be forced to unlock the secrets of the facility.

Appearances
The Big Empty is mentioned in the Fallout: New Vegas add-ons Dead Money and Honest Hearts, and appears in the DLC Old World Blues.

It was to appear in Van Buren, but in later development was merged with the Leavenworth prison into the Tibbets Prison facility. Tibbets would occasionally still be referred to as the Big Empty by developers in design documents.

Behind the scenes

 * The Big Empty is one of two known facilities to have done research on electrical weapons. The other was the Secret Vault, Vault-Tec's private vault.
 * The Big Empty appears to have used geodesic domes in its construction.
 * There are three geographic features called "Big Mountain" in the southwest: Arizona's Black Mesa, a peak in Nevada's Black Rock Range, and Big Mountain Ridge, in Los Angeles County, California.