In the Fallout series, the vaults were built to protect human life from atomic bombs, providing safe underground shelter for years until the surface world was once again safe to be inhabited. At least that's what the Vault-Tec Corporation told everyone. In truth, most vaults were built to perform sinister, cruel, and occasionally funny experiments on the unsuspecting inhabitants.
There are a lot of vaults in the Fallout series. In this list, I'm only including actual vaults you can visit in the existing Fallout games on PC, and disregarding vaults only referenced in passing or those deemed non-canon by Bethesda (such as in Fallout: Tactics).
Considering the amount of evil and suffering involved in Vault-Tec's vaults, it's hard to say what makes one vault 'better' than another. I mostly based these rankings on how interesting they are to visit, how memorable they are to explore, and how interesting the lore surrounding them is. Here are the vaults from the Fallout series, ranked from worst to best.
Vault 88 (Fallout 4: Vault-Tec Workshop)
Vault 88 was never completed, but that's where you come in. Added with Fallout 4's Vault-Tec Workshop DLC, it's ostensibly a chance to let you become Overseer and perform your own experiments.
Unfortunately, it winds up essentially being just another settlement, albeit one with vault-themed building options and a lot of room to build. The experiments, however, are a bit on the tame side and don't leave much of an impression, letting you be a bit mean to your dwellers but not truly evil as you have them power generators by riding stationary bikes or by serving them tainted cola. It's not the Overseer experience I've always dreamed up.
Vault 111 (Fallout 4)
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Cryogenics doesn't sound like a bad idea at all for surviving an atomic war underground, but only if you actually inform the vault residents about it first. Naturally, Vault-Tec didn't, instead saying the pods were for decontamination. Surprise! You're an ice cube.
Due to a short-sighted lack of supplies, the non-frozen staff eventually staged a mutiny. Over 200 years later, one frozen resident (you) awoke long enough to witness their spouse being murdered and infant son abducted. Another quick 60 or so years passed, and the resident awakened again to find themselves the sole survivor of the cryogenic experiment. Other than the kick-off to the main quest, though, there's not much reason to hang around the somewhat dull Vault 111: not when there's the settlement of Sanctuary Hills just outside.
Vault 95 (Fallout 4)
Vault-Tec set up Vault 95 as a rehab center for drug addicts, and did an admirable job carefully and thoughtfully treating its residents' addictions. Nice! Then, five years later, it popped open a secret hatch filled with a bunch of drugs just to see what would happen. Not nice!
Many of the addicts relapsed, others fought and killed one another (the Vault-Tec jerk who opened the drug hatch was killed too, at least), and it eventually became a Gunner hideout. Apart from clearing out Gunners, you can also use Vault 95 to cure your companion Cait of her Psycho addiction. Nice!
Vault 3 (Fallout: New Vegas)
Vault 3 was a control vault, scheduled to open just 20 years after the bombs fell. The residents, however, weren't eager to expose themselves to the dangers of the outside world and quite sensibly kept it locked longer than was planned. They even managed to stay indoors without everyone killing each other. Weird!
There wasn't even a sinister experiment (as far as we know) taking place within the Vault, which therefore makes it one of the more successful yet least interesting vaults in the series. After a malfunction in the vault's water system, however, the people of Vault 3 opened its door and were promptly slaughtered by a collection of drug-addled Raiders called Fiends. When you visit you'll get to exact revenge by wiping out the Fiends and freeing some of their prisoners.
Vault 34 (Fallout: New Vegas)
Vault 34 was spare on living quarters which eventually became an issue due to massive over-population. Also, Vault-Tec filled it with a ridiculous amount of weapons—and an armory door that couldn't be locked. Do you see where this is going? Riots broke out in attempt to plunder the armory, leading to damage to the vault computers, a radiation leak, and a whole lot of inhabitants being turned into ghouls. Whoops!
In addition to learning the story of the vault, there's plenty of weapons and ammo still left, making it a worthwhile visit.
Vault 19 (Fallout: New Vegas)
Red vs Blue: a war as old as time. Vault 19 was separated into red and blue sections accessible only to those with the correct color keycards, most likely as an experiment to see how the different colored teams might interact with (turn on) each other.
Unfortunately, a sulfur leak from caverns below the vault caused the inhabitants to abandon it before they could completely devolve into the violence and murder that seems to be the desired outcome of many of Vault-Tec's experiments. The vault was partially occupied later by Powder Gangers. Make nice with them and they're be perfectly friendly, or you can blow the whole place up with C-4. As with so much of Fallout: New Vegas, it's entirely your choice.
Vault 92 (Fallout 3)
Vault-Tec invited the world's most talented musicians to Vault 92, hoping not just to preserve the human race but also its musical culture and history. Ha ha! No, they really invited them to use them as unwitting test subjects for white noise experiments in an attempt to create a legion of obedient super soldiers.
Hold on to your eyebrows, because they're about to shoot up in surprise: it all went horribly, horribly wrong. The white noise eventually drove the test subjects into fits of extreme rage, which isn't a terrible side-effect if you're building super soldiers. Not so useful is the fact that they couldn't be controlled. There was eventually a mass slaughter in the vault, compounded by the collapse of a portion of the vault walls, which allowed a swarm of mirelurks to enter. Mirelurks are gross and their clicking and clawing isn't music to anyone's ears.
Vault 75 (Fallout 4)
Vault-Tec may have topped themselves for sheer evil with Vault 75. Supposedly built as a safe place for schoolchildren, the kids who took refuge there were separated from their parents upon entering, and the parents were quickly executed an incinerated. Children were tortured and tested to determine which had the 'best' genes, and at age 18 those genes were 'harvested' for the next generation in a revolting attempt to create a master race, if you will. Those not up to snuff were snuffed out like their parents.
At some point the subjects of the tests learned what was happening and rebelled, killing the scientists and escaping. Wherever those kids wound up, it's gotta be a better place than Vault 75. The vault is now inhabited by Gunners, though the Brotherhood or Institute may show up, and while you're too late to help the long-departed children of Vault 75, you get the satisfaction of making sure the 'research' conducted here never falls into the wrong hands.
Vault 22 (Fallout: New Vegas)
Seemingly a decent vault with an admirable goal, 22 was staffed with scientists who would undertake agricultural studies and subsist on the plant life grown inside. Unfortunately, as sometimes happens with videogame scientists, they made an oopsie and a fungus meant to control pests wound up becoming pests.
The spores of the fungus infected the human population, turning them into horrible plant monsters. It's a deadly and harrowing battle through the vault as you fight these lightning-fast creatures along with giant Venus Flytraps and mantises. At least you get to blow the entire lab up to make sure they don't escape to the surface world.
Vault 15 (Fallout, Fallout 2)
One of the few vaults you can visit in two different games, Vault 15 was an experiment to see how a population composed of a variety of cultures and backgrounds would get along when crammed into a confined space together for decades. In short: they didn't, and when the vault opened 50 years later, the dwellers split into several warring factions of raiders, plus one group that eventually form the NCR.
Though the vault has been stripped and pillaged, it's still being fought over by a few different factions. At the very least, you can bring a little peace to the contested vault by dealing with the raiders who have been kidnapping people living at the entrance, and brokering a deal between the locals and the NCR.
Vault 81 (Fallout 4)
Entering this vault is an absolute shock because it's filled with… normal, well-adjusted people living their lives.
Vault 81 was intended to find the cures for all known diseases by secretly experimenting on its inhabitants—by infecting them with those diseases. However, in a surprising twist, the Overseer of Vault 81 wasn't actually an evil prick and prevented most of the medical scientists from ever entering the vault. She then sealed off the rest of the scientists from the population permanently. The scientists were pretty good sports about it, honestly, and carried on studying diseases for the rest of their lives, and not on unwilling human subjects. Best of all, they created Curie, a very nice robot with a French accent who can accompany you on your travels.
Vault 118 (Fallout 4: Far Harbor)
Up for a murder mystery? Built under a hotel, Vault 118 was never completed and its experiment (to house Hollywood hotshots in the lap of luxury and working class stiffs in cramped quarters) was never realized. There's still plenty of drama. A robobrain has been murdered, and when you arrive you get to play detective, question the suspects, and finally, make an accusation. It's fun, and there's some great loot to be acquired, too.
This vault and quest is a contentious one in the Fallout community, though—it bears a lot in common with a mod called Autumn Leaves for Fallout: New Vegas, which also contains a robot-themed murder mystery and a few other details that feel suspiciously similar. The modder didn't seem too bothered either way, but would like at least to be credited. As for Bethesda, it's denied copying the mod altogether.
Vault 114 (Fallout 4)
Leave it to Vault-Tec to drop the ball on their one good idea. Vault 114 was advertised to rich politicians and the wealthy elite, who would arrive to find themselves crammed into tiny apartments with shared bathrooms and at the mercy of a deranged, pantsless, Abraxo-eating Overseer named Soup Can Harry.
Unfortunately, the vault was never completed and it appears no one ever moved in. On the plus side, this is the vault where you first meet Fallout 4's best companion, robotic gumshoe Nick Valentine, and face off against gangster Skinny Malone. Plus, you get to listen to Soup Can Harry being interviewed on holotape—a definite bonus.
Vault 106 (Fallout 3)
This is pretty a unimaginative experiment by Vault-Tec standards: 10 days after the vault was sealed, psychoactive drugs were pumped into the air supply. Everyone went crazy and killed just about everyone else. So, uh, yeah. Crazy drugs make people crazy. Good work, everyone!
It's also a creepy and disturbing place to visit. While exploring you'll inhale some of the drugs still in the air and trip balls, your vision flipping between a pristine and populated vault and a rusting and ruined one. You'll imagine your father, Butch, and other residents of Vault 111 are present as well. While they're attacking you (and then vanishing when engaged) you're also being attacked by real deranged residents of Vault 106. It's a jarring and memorable experience.
Vault 12 (Fallout)
Radiation: how does it work? Vault-Tec decided to find out by herding a thousand people into Vault 12 and then making sure the door wouldn't close when the bombs fell. Sorry-not-sorry, citizens!
The results of the experiment: radiation is pretty bad for humans, as it turns out. Citizens were transformed into disfigured ghouls and glowing ones, which largely populate the vault when you arrive. The true revelation of Vault 12, however, is that not all ghouls are simply monsters. Ghouls can be good people, and despite their tragic circumstances they carry on with their lives, a tradition that has carried through the rest of the Fallout series. Many of the ghouls from Vault 12 went to the surface and eventually founded a ghoul-town on the called Necropolis.
Vault 11 (Fallout: New Vegas)
The social experiment in Vault 11 was a damn grim one. Residents were told that every year, they would have to sacrifice one resident or they would all die. You even get to visit the sacrifice chamber, where a filmstrip is shown to the unlucky lamb stressing how important their sacrifice was for the greater good—after which the walls slide open and a score of robots and turrets open fire. The actual sad truth of Vault 11 was that if the citizens had chosen to stand together and refuse the annual sacrifice, nothing bad would have happened to them.
But these are human beings we're talking about, so naturally they went with the sacrifice option, which led to other bouts of infighting, plotting, back-stabbing, and murder. In the end, only five inhabitants were left, and discovering that all the killing had been done for nothing, they considered the only 'logical' option: killing themselves. They didn't, though, because one of the five shot the other four dead. What a great group of people, huh? Of all the vaults, this one sounds like human nature was pretty accurately depicted.
Vault 8 (Fallout 2)
Vault 8 contained nearly 1,000 inhabitants and was intended to remain locked for 10 years, after which its residents would attempt to rebuild society on the surface. What went wrong? Well, nothing, really. In fact, Vault 8 was a smashing success, which shows just what can be accomplished when you don't perform a bunch of horrifying secret experiments on a bunch of people trapped underground.
Vault 8 eventually formed the foundation for Vault City, a sprawling community that was also highly successful, though its isolationist habits eventually led to its downfall. The vault itself remained mostly in good shape, however, housing an excellent medical center, plus a host of quests and characters.
Vault 101 (Fallout 3)
It's hard not to have a few fond memories of Vault 101: in Fallout 3, it's where you're born and grow up in a series of scenes that constitute the tutorial. There were so many good times: shooting your first radroach with a BB gun, watching a robot cut a cake with a buzzsaw on your birthday, passing your GOAT test, bludgeoning that asshole Butch to death with a baseball bat... and, oh yeah, realizing your shitty dad lied to you for years and then abandoned you to almost certain death. So many memories!
The ghastly truth of Vault 101 was that it was supposed to remain closed forever. It didn't, making it another of Vault-Tec's expensive failures. But the experience of beginning the game here, from the very moment of your birth to your eventual violent and dramatic escape, makes this one of the most memorable vaults in the series.
Vault 13 (Fallout, Fallout 2)
What we know about the true purpose of the vaults—the secret and diabolical social and science experiments they were constructed for—begins with Vault 13. Its purpose was to remain closed for 200 years, not to protect the inhabitants from the dangers of the surface world but to study the effects of prolonged isolation upon its residents.
When an element of its water purification system failed, Vault 13's Overseer began sending explorers out to locate a replacement. When the Vault Dweller returned the Overseer hailed him as hero but then exiled him, worried that other vault dwellers would want to leave the vault and join the outside world. The experiment in Vault 13 was to be protected even if it meant banishing its savior. The theme of hiding the truth from those who inhabit the vaults, and denying them free will under the guise of protecting them is carried on from Vault 13 through the rest of the Fallout series.
Vault 112 (Fallout 3)
A great way to pass the time underground is with your body in cryostasis and your mind plugged into a virtual reality simulation that creates an idyllic utopia you can happily inhabit forever. Unfortunately, this is Vault-Tec, so under the tree lined streets and white picket fences of Tranquility Lane lies a torturous and unending Hell. The Overseer, Stanislaus Braun, is a sadistic madman who uses the simulation he created to stalk and virtually murder the vault's inhabitants. Then he wipes their memories and murders them again. Repeat roughly forever.
You get to take part in the trippy simulation while being directed by Braun to torture the other residents both psychologically and physically, from making a little kid cry to straight-up stabbing everyone to death while dressed as an adolescent slasher. Freeing everyone from Braun's endless torture, though, requires killing them in the real world: ultimately an act of mercy.
Vault 21 (Fallout: New Vegas)
What happens in a tin can underneath Vegas stays in a tin can underneath Vegas, except in the case of Vault 21. Vault-Tec, in its infinite wisdom, decided to fill a vault completely with compulsive gamblers. Surprisingly, the gamblers-only society seemed to have done fairly well, all things considered, with games of chance being used to settle differences. Eventually, Robert House set his sights on a takeover of Vault 21 and did a bit of remodeling.
Vault 21 was turned into a casino and hotel, which is a far better fate than most vaults experience. The door was even appropriated into a sign for the hotel, and it's refreshing to visit a vault with actual life in it instead of just a rotting tin can of death like so many others. You can even acquire a personal and permanent hotel room there.
Vault 108 (Fallout 3)
When Fallout fans discuss the various vaults, it's never without a mention of Gary. And I'd really hoped to come find a vault that was better than Gary's, just to shake things up a little. But I'm with everyone else on this. Gary. Gary? Gary!
Vault 108 was an experiment to determine how people function in a crisis with a lack of leadership and an overabundance of weapons. The vault was assigned an Overseer who would die of terminal cancer within months, outfitted with a heavily stocked armory, and given a malfunctioning power supply. What would happen in the vacuum of leadership when the lights went out and guns were everywhere?
We don't really know, honestly, because oddly enough a cloning chamber was included in Vault 108. That doesn't really fit in with the leadership experiment in any way that I can tell, but it does bring us to Gary. (It brings us to several Garys, actually.) Gary was a resident of 108 who was cloned multiple times, with each resulting Gary only able to speak the word "Gary" and each Gary more violent than the last Gary—at least to any non-Garys. Gary was cloned over 50 times, which was a few too many, as ultimately the only survivors of the Vault are a handful of variously numbered Garys—and they are not at all happy to meet you.
It's certainly one of the more memorable locations and encountering Gary after angry Gary is a surreal experience. Vault 108 isn't the only place Gary appears, either. Interestingly, Gary 23 somehow escaped and was found by the Brotherhood in the Operation: Anchorage expansion. They cut off his arm to remove his Pip-Boy after growing frustrated by his inability to say anything but his own name. Another Vault in Fallout 4 has a number of alphabet blocks that spell out Gary—perhaps one escaped Gary had children?