In the alternate timeline of the Fallout universe, the United States government implemented Project Safehouse as a means to provide security and shelter for its population in the event of a nuclear holocaust. And so it was that pre-war super corporation Vault-Tec was contracted to construct a series of state-of-the-art underground bomb shelters, intended to preserve the people and materials necessary for rebuilding civilization. These shelters were known as vaults.

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The purported and publicized purpose of the vaults is straightforward enough. But between the complex technology required to operate them and the conspiratorial relationship between Vault-Tec and the government of the United States, to say that there's much more to them than meets the eye would be a woeful understatement. To illustrate, here are ten little known facts about Fallout's iconic subterranean slices of paradise.

10 400,000 Vaults Would Have Been Necessary To Save Everyone

Fallout 4 Pre War House And People

In the Fallout canon, the population of the United States was estimated at 400 million people prior to the nuclear exchange of the Great War. At their absolute maximum capacity, a typical vault was designed to shelter roughly one thousand people.

Given these estimates, running the associated calculations, this means that no fewer than 400,000 Vaults would've been necessary in order to save the entire population from nuclear fire. To contextualize that, Vault-Tec only built 122 Vaults on-record.

9 A Lot Of Them Sealed Without All Of Their Assigned Inhabitants

After the Vaults were completed, Vault-Tec promptly began to run test drills in order to gauge and streamline the efficiency of their systems. Needless to say, quite a bit of testing was in order, given the human elements and cutting-edge technology that was involved.

Unfortunately, these repeated tests would result in a "Cry Wolf" effect, with fewer and fewer vault inhabitants turning out as they continued. Even less fortunately, this would result in many dismissing the real deal as nothing more than another drill on the day that the bombs actually fell.

8 Only 14% Of Them Were Meant To Fulfill Their Promised Purpose

Anyone familiar with the Fallout canon is likely well aware that Vault-Tec, in collaboration with the US shadow government known as the Enclave, designed quite a few Vaults that were intended to carry out a variety of wild and sometimes frightening experiments on the populations inhabiting them.

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But you might not be aware of just how few of them were actually made to carry out their original purpose. Out of the 122 Vaults that were made for the public, only seventeen of them were made with the sole aim of preserving human life. The rest were intended to run some form of social experiment.

7 Some Of The Vault Experiments Were Outrageously Cruel

The inhabitants of the experimental vaults were typically unaware of the fact that they were being experimented upon. Some of them were purely ridiculous, such as a vault housing only one man and a crate full of puppets. Others even seemed utopian in nature, such as Vault 94 testing the principles of non-violence and communal living in harmony with nature.

Others, however, were incredibly dark, if not despicable. For instance, Vault 11's population was directed to sacrifice one of its own to the vault each year, or else it would shut off its life support systems. After many, many years, the remaining inhabitants would refuse. Instead of shutting down the life support systems, the vault played a message congratulating them for their selfless sense of humanity. Only five of them remained to hear it.

6 Getting Into A Vault Was Incredibly Difficult

Although the vaults were up and running, their collectively inadequate capacity when compared to the entire country's population meant that entry was a rare and coveted commodity. It was likely an expensive prospect for most.

There were some notable exceptions. The opening events of Fallout 4 showcase the population of Sanctuary Hills evacuating to their local vault, shedding an expository light on how many people were completely barred from entry - including Vault-Tec's own employees. Contrasting this is the Sole Survivor's ease of entry, with their family being admitted by virtue of Nate's service in the Army.

5 There Were Secret Vaults

In addition to Vault-Tec's known underground shelters, a number of powerful entities such as various government offices, wealthy corporations, and even Vault-Tec itself commissioned private, secluded Vaults for their own purposes. Fallout 76's Whitespring Bunker is a sterling example.

Though its canonical specifics are questionable, Fallout: Brotherhood of Steel allows players to visit one of these secret Vaults. Located in Texas, this vault was meant to provide shelter for Vault-Tec's very own top ranking executives and scientists, allowing the company to survive and continue developing technology after the bombs fell.

4 The Majority Of Them Failed Shortly After The Bombs Fell

Although reportedly able to provide life support for nearly a single millennium, and boasting a human life expectancy of ninety-three years, most of the vaults failed in one way or another shortly after the atomic exchange of the Great War.

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This was largely on account of the various experiments being performed on the populations of most vaults, as they introduced factors that made survival unlikely, if not outright impossible. Those few control vaults, or those that lacked any experimental tampering, mostly performed as expected.

3 They Were Built As Far Out As Canada

Vault boy giving thumbs up as happy people enter the vault

The vaults, both public and private, were presumably peppered across the entire United States. States with confirmed vault locales included California, Nevada, West Virginia, Maryland, Maine, Massachusetts, and Virginia. Texas, Colorado, and Washington join the list when considering sources with dubious canonical authenticity.

A letter sent to a rejected Vault applicant can be found in Fallout 3 that indicates vault projects also existed in Oklahoma, and perhaps most surprisingly, Canada. Whether or not these vaults were actually completed isn't confirmed, but considering Canada was annexed by the US during the Fallout timeline, it makes sense.

2 The Overseer Could Spy On Anyone At Any Time

Although the role saw some variation between the experimental vaults, the position of Overseer was generally one of immense power. The Overseers controlled access to rations, supplies, weapons, and could control most of the vault's functions from their offices.

Perhaps most disturbing was their ability to survey the goings-on practically anywhere in the vault, and at any time, utilizing their Eye-On-You security cameras. These creepy electronic peepers are mentioned at the Vault-Tec exhibit inside of the Museum of Technology in Fallout 3.

1 Vault 8 Succeeded & Blossomed Into A Vibrant City

Though the history and lore behind the vaults is riddled with grotesque experiments, strange anomalies, and outright failures, there are a few rousing success stories to be found among them. One such story is that of Vault 8, a control vault located in Nevada.

Virtually everything proceeded as intended for its lucky inhabitants. It received its scheduled all-clear signal and opened its doors to the wasteland, and its inhabitants utilized its existing technology as the central basis for the small city that sprung up around it. Its inhabitants were a bit xenophobic and distrustful of outsiders, but it nonetheless flourished as a technological marvel compared to most other vestiges of post-war civilization.

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