The Vault - Fallout Wiki

We've Moved! Just as Gamepedia has joined forces with Fandom, this wiki had joined forces with our Fandom equivalent. The wiki has been archived and we ask that readers and editors move to the now combined wiki on Fandom. Click to go to the new wiki.


The Vault - Fallout Wiki
Master of the Mojave.png
Fallout: New Vegas locations project
This article is within the scope of the Fallout: New Vegas locations project. This project is dedicated to standardizing Fallout: New Vegas location articles. If you want to participate, please check the project page.
Icon disambig.svg
This page is about the Big MT as it appears in Old World Blues. For the Big MT as it would have appeared in Black Isle's canceled Fallout 3, see Tibbets Prison.
Big MT
FNV Big MT Panorama 1.png
FNV Big MT Panorama 2.png
Icon military.png
180 degree panoramas of Big MT, from the top of the Think Tank dome
SectionsThe Sink
FactionsBig MT company (pre-War)
Think Tank
QuestsOld World Blues
Big Empty.jpg
Gametitle-FNV DM.pngGametitle-FNV HH.pngGametitle-FNV OWB.pngGametitle-FNV LR.pngGametitle-VB.png
Gametitle-FNV DM.pngGametitle-FNV HH.pngGametitle-FNV OWB.pngGametitle-FNV LR.pngGametitle-VB.png

Big Empty's a treasure box, a scientific graveyard of Old World misery. Like the Sierra Madre... there's treasures there, sleeping. Some, awake. The Holorifle, the Saturnite alloy... the hologram technology, hibernation chambers, Securitrons, the collars... ...even the suits attached to those things stalking the Villa... that's only the surface of what's there. Right now, the Sierra Madre is what I want.

Elijah, Dead Money

The Big Mountain Research and Development Center, alternately known as Big MT and the Big Empty, was a privately owned pre-War defense contractor and research center located in the Southwest Commonwealth. Originally, Big MT got its name from the mountain that was above the underground center, but that mountain was vaporized sometime before the war and the underground center became an open-air center. It serves as the game-world for the Fallout: New Vegas add-on Old World Blues.



The Big MT Research and Development Center was originally built inside a cave system running underneath a large mountain peak (hence the name). Their goal was to build the future of mankind and create the technology of tomorrow without restraints, either moral or technical. It welcomed some of the most gifted pre-War scientists, who plumbed the depths of many experimental technological fields. The research conducted within was as groundbreaking as it was unethical, conducted in part on living humans (both American volunteers and Chinese-American detainees). Big MT even included a concentration camp of its very own, safeguarded by lucrative contracts with the U.S. Army, such as the X-42 giant robo-scorpion.[1] However, due to budget cuts in the later years of its operation, Big MT had to improvise alternate means of funding and research. The executives began to strike deals with third parties, exchanging experimental technology for funds and other privileges. Due to budget cuts, they even began assassinating non-military targets (Project Hare) to procure research subjects, and exhuming buried US citizens (Project Burke) to procure test subjects.[2]

Due to a failed experiment conducted in the Y-0 research center, the mountain above the center was vaporized, leaving behind a giant crater and the exposed facility. This catastrophe did little to phase the researchers, and the efforts in pushing the boundaries of science continued unabated. The new land exposed by the explosion was adapted for scientific purposes: new facilities were established, both above- and below-ground, including an artillery test field and a test town. Under the guidance of its six gifted executives, named together the Big MT "Think Tank" executives (known only as Klein, Mobius, Dala, 0, Borous, and 8; their original names are long lost), the facility gave birth to new technologies, such as the Saturnite alloy, next generation hazmat suits, new models of cyberdogs, an intelligent stealth suit, holograms, and many more. At the same time, many new horrors were also born in the laboratories of the Big MT: cazadores, nightstalkers, mutagenic plants, ambulatory corpses, previously unknown toxins, and other fearsome creations. Both types were sold to private parties in exchange for certain favors: Frederick Sinclair obtained various experimental technologies (including even the prototype matter conversion machines) in return for allowing Big MT to use the Sierra Madre as a proving grounds,[3] a decision that backfired catastrophically when the experimental technologies turned on the casino inhabitants, dooming them. Such an event was not unprecedented either: the town of Hopeville suffered devastating storms as a result of a Big MT meteorological experiment in another such exchange.

The scientists' cooperation wasn't entirely frictionless. During one particularly heated dispute with the future Doctor Mobius threw The Sink's personality chips off the dome's balcony. The Big MT staff picked up the various holodisk chips and stored them in existing facilities, and that of the Sink Central Intelligence Unit was personally recovered by the future Doctor Klein.

The Great War and its aftermath

When the Great War came, it didn't stop the research efforts; it merely put them on a different rail. Mobius worked on predicting the post-holocaust economic systems. A new project was also started, with the purpose of preserving the Big MT "Think Tank" executives by transforming them into a special brain bot named after their group, allowing them to continue their work at Big MT indefinitely, but "reprogrammed" to forget a part of their personality and their name, by giving them a new one, enforcing the recursion loop in their new perception programming. With no body to stand in the way, their research continued, becoming more sinister and debauched as the years went by.

Eventually, the remaining human staff dispersed or was killed by the increasingly out-of-control facility like the escape of the cazadores and the nightstalkers. Only the six think tanks remained in the Big MT. Mobius, tired of the think tank's endless and horrible experimentation, thinking that "the world isn't ready for that kind of too-far-thing-taking" and believing that the think tanks had finally lost what remained of their humanity, erected a radar fence - a kind of radar-guided repulsive field - around the perimeter of Big MT to prevent the disembodied brains from escaping into the wasteland, and destroying what little remained of humanity with his colleagues' planned experimentation on a new "fertile testing ground".

After a severe dispute with Klein, Mobius hacked his colleagues' shells, causing them to forget large portions of their personality and substituting their name with a new one, reinforcing the recursion loop already programmed before. Furthermore, he hacked the databanks of his colleagues, reprogramming their chronometers, geometers and cartography programs, making them to lose the sense of time and history. He also forged several facts to focus the Think Tank's attention on himself: that his robo-scorpions consume intelligence from brains (creating the fear to go outside the central Big MT's dome), that he was exiled for a crimes too heinous to remain in recorded memory, and a belief that Big MT is all that remains of the world, that nothing exists outside. In the end, his tampering created a mangled, disjointed versions of his former colleagues. Disgusted by his actions against his friends, he erased some parts of his own memory to ease his conscience, like this event (though not permanently, as certain phrases could reawaken the memories) and knowledge his pre-War creation, the robo-scorpion.

Soon after, Mobius removed himself to the X-42 robo-warfare facility (renamed the "Forbidden Zone"), where he began to "re-create" the robo-scorpion, inspired by radscorpions wandering into Big MT. His new creation retained all features of the pre-War model: a tail-mounted energy bolt blaster, eyes systems allowing him to see through them, remote control and public address systems allowing him to monitor the Big MT. Fearing that the radar fence would not be sufficient to hold the mad scientists inside the crater, he set up a repeating threat message to be broadcasted to the Think Tank. The aim was to instill fear and prompt them to focus on retrieving technologies that would allow them to depose Mobius. Then, the Big MT fell finally silent, became the arena of an increasingly demented, insane struggle between Mobius and the Think Tank. The latter remained inside the dome, ever fearful of their self-appointed warden and his scorpions.

Big MT had few visitors, the sheer size of the crater serving as its best camouflage: most wastelanders assumed the ragged edges to be remnants of a massive nuclear explosion and avoided it altogether. The unfortunate few who wandered in disappeared forever, apprehended by robots and lobotomized by the think tanks to act as organic automata, maintaining the decaying facility and protecting it against scavengers. Over the years, it ironically became known in the wasteland as the "Big Empty", a place where nothing exists. Its size and aura of mystery blocked the establishment of trade routes and reliable supply caravans between the Boneyard and New Vegas, a fact that proved crucial to the Caesar's Legion survival immediately following the First Battle of Hoover Dam, as the NCR was unable to reinforce its army quickly enough.

The Visitors

Even if the facility's security was almost perfect, three people were able to elude the think tanks and survive the horrors intended for them: Elijah, Ulysses and Christine Royce.

Elijah came to the Big Empty in search of weapons that would allow him to destroy the NCR and everyone who would oppose him in the creation of a new Brotherhood of Steel order. Elijah scoured the facility for technologies that would be of use to him in his endeavor. Namely, after learning of the Sierra Madre from Ulysses, he started gathering equipment that would allow him to crack the casino. The most important and sinister of these were the concentration camp detainment collars, that he experimented with during his stay.[4] He also took a unusable holorifle prototype,[5] perfected afterward thanks to the holograms of the Sierra Madre.[6]

Ulysses came to Big MT in search of knowledge, to learn what makes and breaks nations, what would allow him to reawaken America, the Old World. Christine Royce followed Elijah, tasked with killing him for the crimes committed against the Brotherhood of Steel.

Of the three, Christine was the only one who did not escape unscathed. Captured by Big MT robots following a disastrous skirmish at Little Yangtze and pitted against Elijah who sent the survivors of Little Yangtze against her like walking bombs, she was subjected to horrific experiments in the Y-17 medical facility conducted by some Mister Orderly and Y-17 trauma override harnesses and with a Mark IX Auto-Doc. These experiments permanently damaged her brain, destroying her ability to read and write fluently. She was saved from certain death by Ulysses, who destroyed the entities and nursed her back to health in his camp in Big MT. Afterward, he talked to her about philosophy and his desire to go into the X-17 meteorological station and speak with the Think Tank. Ulysses had come to Big MT tracking storms from the Divide that had to have been man made; he confirmed their source when he found the X-17 meteorological station.[7]

At some point after Elijah spoke with the Think Tank, this made the Think Tank doctors question their perceptions regarding the outside world. The Think Tank began to doubt that their world was as small as they had perceived, bringing new ideas to their minds. After Ulysses and Elijah made contact, at which point Ulysses directed him to the Sierra Madre, Ulysses too spoke with the Think Tank, particularly Dr. Klein, and asked a lot about history and civilizations. Ulysses asked a dangerous question: "Who are you, that do not know your history?" After Ulysses showed them the Old World flag, the Think Tank eventually remembered many past events, especially that there is a world outside the Big Empty, a world with ideas and possibilities for experimentation. Dr. Klein regarded the question as too dangerous, and, as it reminded him too many past events, he subsequently deleted it from his memory. After coaxing the answers, he wanted out. Ulysses returned to his camp to say farewell and pass information on to Christine concerning Elijah; he left Big MT and continued his journey onward to the Divide.[8]

Elijah was the only one who left the Think Tank a parting gift. After being apprehended by Dr. 0 and Dr. 8, he hacked them both within minutes, permanently damaging 8's voice module and leaving destruction in his wake. He left Big MT on a cargo train, and then crashed the remaining trains in tunnels leading out of the facility. During these events, Mobius observed, even the conversation of Ulysses and Elijah with the Think Tank, rendered the inability to act on anything, and his fears grew surrounding the future actions of the Think Tank.

Some time after the three left permanently, the Think Tank installed a pacification field in The Think Tank central area, preventing anyone without a brain to have hostile impulses. Afterward, to see if there really was something outside of Big MT, they sent a satellite prototype with a unique charge of teleportation outside of Big MT which crashed in the Mojave Drive-in in the Mojave Wasteland. It emitted a signal in the form of jazz music, dubbed the mysterious broadcast. The Courier arrived, just after having been guided by the signal. The Courier inspected the satellite during the night, triggering the unique teleporter onboard the satellite and thereafter, was transported to the Big MT.

Afterwards, The Courier was taken to The Sink in preparation to become a lobotomite; but due to the gunshot wound from Benny causing a cranial injury in just the right place, it was enough for the Sink Auto-Doc to change its programming to fix the problem, improving the cranial extraction procedure. However, in the process, it was necessary to replace the spine and heart with synthetic organs. With the Courier's brain procedural data, the Think Thank would be granted the knowledge to modify their cranial selves into hosts to slip past the radar fence and leave Big MT. However, after the Think Tank extracted it, they degraded into bickering amongst themselves. Mobius saw an opportunity to take the Courier's knowledgeable brain and flushed it down a pipe that led to the "Forbidden Zone." With the desire to escape the crater with their brain intact, the Courier was obligated to help the Think Tank against Mobius by retrieving three pieces of technology, changing the future of Big MT forever.


Originally meant as a beacon of new hope for humanity, Big MT eventually created a vast number of technologically astounding, although horrifying creatures and machines, several of whom have made the Mojave Wasteland their home and killing grounds. Big MT's "legacy" includes:


Big MT is dominated by the central dome named The Think Tank, which is connected to outlying facilities by numerous walkways, pipes, and conduits.

To the north lies the rail line that passes into Big MT via the Big MT north tunnel before splitting into two lines that run toward the east and west tunnels. Near the north tunnel is the X-42 robo-warfare facility, an important facility even with a dome; later known as the "Forbidden Zone", the lair of Dr. Mobius. Other notable facilities include the Signal Hills transmitter, the Saturnite alloy research facility, the X-22 botanical garden, and the X-17 meteorological station. Just north of the western train tunnel are the Little Yangtze concentration camp and the construction site.

To the east, along the eastern rail spur, lie several notable facilities, including the X-8 research center, the X-7b "Boom Town" target zone, the Securitron de-construction plant, the hazmat testing ground, and the waste disintegration platform.

The western portion of the crater is dominated by the X-66 hexcrete archipelago, a collection of hexagonal concrete structures that vary in size from small platforms to towering monoliths. Among the hexcrete structures are several facilities, including the X-13 testing facility, the Z-43 Innovative Toxins plant, the Z-38 lightwave dynamics research building, and the X-7a "Left Field" artillery launch.

In the southern portion of the crater is Higgs Village, which contains the former homes of the Think Tank within a large, hangar-like structure. It is flanked by the X-12 research center and Y-17 medical facility.

This is not an exhaustive list of locations within Big MT, but notes some prominent facilities visible from the balcony of The Sink, Dr. Mobius's former apartment, located atop the central dome. For a complete list of locations, see locations in Old World Blues.

Force field restricted locations

Many facilities require an upgraded sonic emitter to gain access to the true secrets that lie within. Without disabling the force fields, exploration only scratches the surface of what's inside.


  • Though many of the pipes criss-crossing the Big Empty can be used to traverse the area by walking on top of them to avoid some enemy attacks, they are also heavily mined.
  • Unlike in the Mojave Wasteland and Zion Valley, all enemy creatures and characters in Big MT are part of the same faction, and will not attack each other.
  • Venture beyond the perimeter of Big MT and you will receive a warning. If you stay beyond the perimeter you will be automatically teleported back to The Sink Balcony. This happens with no penalty incurred, no health damage, and even if you are over-encumbered. This can actually be used to the players advantage as an easy way to get back to The Sink when normal fast travel may not be permitted (assuming you are near the perimeter, of course).
  • It's mentioned by Joshua Graham, and later Ulysses that Big MT is located somewhere near the Divide. Based on what Joshua Graham says its somewhere near State Route 127.

Behind the scenes

  • Much of the Big MT crater was implemented by Megan Parks. Her work included terrain shaping and texturing, static lighting, prop placement and layout, clutter and decoration, as well as creating assets like red crystals, hexcrete towers, path lamps, signage, and glowing elements.[9][10][11]
  • There are three geographic features called "Big Mountain" in the southwestern US: Arizona's Black Mesa, a peak in Nevada's Black Rock Range, and Big Mountain Ridge, in Los Angeles County, California.
  • Project Burke and Project Hare were likely named after the Burke and Hare murders. William Burke and William Hare were serial killers in the early 19th century who provided corpses for medical research by murdering 17 people.


Big MT is mentioned in the Fallout: New Vegas add-ons Dead Money, Honest Hearts, and Lonesome Road and appears in the add-on Old World Blues.

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



  1. Forbidden Zone Dome terminals
  2. X-8 research center terminals
  3. Y-0 research center terminals
  4. Camp survivors and watch tower
  5. The Courier: "I've never heard of the place you're talking about."
    Elijah: "Big Empty's a treasure box, a scientific graveyard of Old World misery. Like the Sierra Madre... there's treasures there, sleeping. Some, awake. The Holorifle, the Saturnite alloy... the hologram technology, hibernation chambers, Securitrons, the collars... ...even the suits attached to those things stalking the Villa... that's only the surface of what's there. Right now, the Sierra Madre is what I want."
    (Elijah's dialogue)
  6. The Courier: "What is this rifle?"
    Elijah: "It is a Holorifle, a weapon I constructed when I arrived... I have since made superior models - and modifications. For now, that tool will have to do until you find other weapons... and I suggest you do, the Holorifle's ammo is limited. Still, it should serve well enough. I fashioned it from the Holograms of the Villa and used it against the Villa's... living inhabitants."
    (Elijah's dialogue)
  7. Ulysses log Y-17.16
  8. Ulysses log Y-17.17
  9. Megan Parks' portfolio
  10. Megan Parks' portfolio
  11. Megan Parks' portfolio
  12. Chris Avellone on Twitter