It's a myth that every billionaire splurges on rare cars or art. But there are some things -- islands, submarines, private rockets -- that your Gateses and Zuckerbergs do tend to whip out their fat, fat wallets for.
If you, too, have just made your first billion, congrats. Here's what you need to buy to fit in.
Billionaires, particularly oligarchs from emerging economies, tend to be on the paranoid side. They tend to buy opulent mansions and then retrofit them for war scenarios (more on that later).
But the ultimate option for billionaires hoping to survive a war, coup or zombie apocalypse? You're looking at it. The self-described "largest billionaire bunker in the world," the Oppidum, built in a secret location in the Czech Republic, is designed for a single buyer.
The condo complex-slash-bomb-shelter includes a screening room, kids' playroom, gym and simulated outdoor spaces.
There's also a meeting room, wine cellar and a pool. In case you're wondering precisely which billionaire has bought this bunker, good news: As of May 2016, there was no reported tenant -- yet.
Lots of millionaires have nice cars. But billionaires do rockets. This one essentially belongs to Amazon's Jeff Bezos, whose Blue Origin venture sent this "space vehicle" up for a spin in late 2015.
The privately-funded Blue Origin employs 600 people and, thanks to an estimated $500 million investment, pretty much belongs to Bezos, lock, stock and booster.
Speaking of Bezos: The Gulfstream G650 costs about $64.5 million. Owners of this plane, or a variant of it, include (through their privately owned companies) the Amazon founder, Larry Ellison and Paul Allen.
The plane maker itself is so elite that reporters must seek permission and state their business before being allowed to use its press handout photos. (This image of a G650 is not one of those photos.)
For a fee ranging from, say, $250,000 to $1.5 million, the top-notch Gaffco Ballistics will turn any billionaire home into a custom, bullet-resistent fortress.
Here's one such Gaffco door, complete with its own gun port.
Here's the exterior of a another Gaffco project. The windows look ordinary, but they can stop bullets from AK-47s.
For an additional, say, $250,000, Gaffco can (and has) equipped billionaire homes with dirty-bomb filtration. In recent months company president Tom Gaffney has kitted out billionaire homes in such far-flung locales as Lagos, Nigeria; Saudi Arabia and Singapore.
This is the Octopus, a super-yacht belonging to Paul Allen. It has a recording studio and two helipads. It hosts parties during the Cannes movie fest. It's worth somewhere north of $162 million.
But the true billionaire toy lies inside its hull...
This is the Pagoo, the heart of Allen's underwater wreck-hunting adventures. It's one of two submarines Allen reportedly has on board. It can dive for up to eight hours and accommodate 10 people.
It's kept in an interior dock on the bottom of the yacht, and maintained, along with the rest of the Octopus, by a permanent crew of 60.
See this guy? He looks ordinary. He is not. The CEO of risk consultancy SR-M, Heyrick Bond-Gunning (as if we could even make that up) provides ridiculously advanced, high-tech security to billionaire clients.
From hacking to physical intrusion to kidnapping, he can -- and does -- address it all, installing fingerprint-activated locks for families, programmable keys for staff, thermal-imaging cameras, panic rooms -- the works.
The price for such peace of mind? Around $1.5 mil.
Here's Goldgenie founder Laban Roomes, whose company painstakingly gold-plates the phones of millionaires.
As for billionaire phones, their communications, along with their Internet activities, are often encrypted by private security consultants.
This bed, reportedly worth about $1.6 million, was designed by Janjaap Ruijssenaars and uses magnets to float. We know of no billionaires who have bought it as of yet, but it's certainly too expensive for mere low-level millionaire.
This is Witanhurst, a massive London home that reportedly includes an elevator just for its cars. It's owned by a Russian billionaire.
Oddly, many billionaires drive pretty ordinary cars -- Audis, for example or mid-level SUVs. But as anyone who watches "Silicon Valley" can tell you, real billionaires have cars with doors that do ... this.
Larry Ellison has owned a version of the McLaren F1, which can fetch millions.
Fact: Few people enjoy backing out of their garages. That's why billionaire garages tend to have these: Turntables. Turn the table, et voila: You never have to back out of a garage again.
As rich-person gadgets go, these are relatively cheap: Jay Leno, a mere millionaire, has one.
Fun fact: Billionaires like to buy islands. Larry Ellison reportedly owns 98 percent of the Hawaiian island of Lanai, which is home to rocks with ancient petroglyphs.
Most billionaires arrange travel via permanent, private staff. But oftentimes that staff turns to companies like Fischer Travel, whose founder, Bill, shown here, has an unlisted number and a waiting list. His company, run by daughter Stacy, reportedly charges a fee just to become a customer.
How much, you ask? As of 2010, it cost $100,000 to become a client, and another $25,000 annually to stay on.
In general, it helps to have investable assets of at least $30 million for Fischer to want to talk to you, but even that doesn't guarantee membership.