Tom Gaffney won’t tell me where he is. We’re talking on the phone and I know he’s on the Upper West Side of Manhattan, but he won’t give away his exact location. Gaffney is on-site installing a safe room—something most of us know as a “panic room”—but revealing the address, even the street, would defeat half the purpose of fortifying a home in the first place. After all, if someone knows you have a panic room, they know there’s something you’re trying to hide or protect.

Gaffney runs a private security design firm called Gaffco Ballistics, based out of a small town in central Vermont. Hailing originally from County Sligo, Ireland, Gaffney still speaks with a rolling brogue, quickly and concisely. He is not in the business to waste time. Gaffney explained to me that his entry into the field came back in 1986. At the time, he was doing work fortifying—or “hardening”—check-cashing facilities in some of New York City’s most violent neighborhoods. For the most part, this meant nothing more than installing bullet-resistant glass, but it soon graduated to building self-enclosed, inaccessible safe rooms inside the businesses.

The safe room, of course, is by no means a modern invention—as University of Cambridge professor of classics Jerry Toner pointed out to me in an interview about burglary in the ancient world—you can see archaeological evidence of safe rooms even in the volcanic ruins of ancient Pompeii. Indeed, urban fortification is all but synonymous with Western history. From castles on hills to concrete bunkers buried six feet beneath the back garden, protective architecture is not an anomaly; it is the rule. Perhaps precisely because of this, the development of contemporary panic rooms is a fascinating tale of design innovation, wealth, occasional paranoia, and brutal necessity. It is a story of crime, self-protection, and architectural extremes—and it’s almost certainly not one you’ve heard before. The first rule of having a panic room is not to talk about having a panic room.

There are two schools of thought in modern panic room design. One of these is well represented by Gaffney’s firm, as well as by SAFE (“Strategically Armored & Fortified Environments”), a Los Angeles–based company run by the husband-and-wife team of Al and Lana Corbi. Gaffco and SAFE both primarily approach home fortification by means of dissimulation and disguise. You are not meant to know you’re in a protected space. Fine woodwork, exacting architectural details, and precise paint jobs deliberately cloak the fact that the room you’re standing in is certainly bulletproof; it is all but guaranteed to be on 24-hour video surveillance; and it is most likely hooked up to a biometric interface for remotely triggering automatic locks and security shutters.

As Lana Corbi explained to me, fortification can be as obvious or well hidden as a client demands; indeed, some of the most protected homes in Los Angeles are the ones that seem not to have a single security guard or camera in sight. These systems are integrated into the house with a careful eye for craftsmanship. In other words, perhaps you’ve even been inside a Gaffco- or SAFE-hardened home; the whole point is that you would only have known if the owner told you.

The other school of thought in contemporary panic room design is best represented by CitySafe, a remarkable operation run by a Vietnam vet and former New Jersey cop named Karl Alizade. Alizade’s work is what you might imagine if you took the same kind of prefab, modular approach to architectural design so often seen in the pages of Dwell magazine, but you added an apocalyptic dose of Mad Max and the Global War on Terror. Alizade makes impenetrable, easily assembled safe rooms, and he does so using a proprietary concrete mix, a patented bolt-together assembly system originally designed for high-security jewelry safes and vaults, and no visible concern for aesthetics. The results are gunmetal gray boxes that would not look out of place in a James Cameron film and that do not even pretend to have a second purpose.

Alizade tests his products against an impressive, if terrifying, range of weaponry, including .50 caliber armor-piercing sniper rounds, rocket-propelled grenades, and even C-4 explosives. In all cases, his safe rooms win. Alizade’s products are designed to resist terrorists and small armies; they will easily repel a neighborhood burglar. His rooms are certified by the U.S. State Department and even underwritten by Lloyd’s of London as functional vaults. Appropriately, Alizade is currently embarking on a shift in business plan to focus on the more drastic needs of his clients in defense, infrastructure, and government. This includes fortifying nuclear power stations, U.S. embassies, and overseas military bases. The beauty of an Alizade safe room is that its panelized assembly requires no welding or even hammering; you could have the most secure room in the city bolted together in your house in near silence, and, next time you move, you can take the whole thing apart and bring it with you.

For his own part, Gaffney is following the market and he, too, continues to push the boundaries—and scale—of home fortification. Gaffney pointed out that it is often inaccurate to refer to a safe room at all, because many clients are now fortifying their entire homes from the outside in. Total home fortification means replacing every window in a Manhattan brownstone with bulletproof glass, for example, and even adding a layer of anti-explosive film; it means nesting ballistic Kevlar plates behind drywall and, in extreme cases, using lead-lined Sheetrock to protect against radioactive attack. More recently, Gaffney added, he has been installing a number of positively pressurized, radiation-resistant, home air-filtration systems. In fact, the steep rise in orders for these in residences throughout New York City has taken Gaffney aback—but the perceived threat of biological and nuclear terrorism has led his clientele to seek adequate protection.

Lana Corbi would call this approach a “safe core”: fortifying not just a closet-sized refuge into which a homeowner can crawl when things go south, but also a scalable network of rooms at the center of the home that can house multiple family members. The safe core could contain a refrigerator, wireless communication equipment, and even a week or two of food and water. Corbi reminded me that it’s not just burglars you might need protection from, but also extreme weather, natural disasters, and prolonged infrastructural failures such as blackouts. A well-prepped safe core is where you can ride out the turbulence—the longer, the better.

If we can use the phrase “panic room,” then perhaps we should really be discussing a “panic house”: a safe blown up to the size of a home, and a home that is truly a castle, a fortress hiding in plain sight on a leafy Manhattan street or steep Los Angeles hillside near you.