Bitcoin is a digital currency, but it still has a physical presence. Private, cryptographic keys need to exists as ones and zeros on actually computer memory. So what do you do if you're a newly-minted Bitcoin billionaire? Maybe you store those crucial codes in a Swiss bunker.
As reported by Bloomberg, bunkers run by a startup known as Xapo, are filled with computer servers that are entirely disconnected from the internet and any other sort of computer network. The company does not actually store Bitcoin, which exists on the public, distributed ledger known as the blockchain. Rather, the vaults store the private, cryptographic keys used to lay claim to particular Bitcoins.
Xapo has vaults on five continents, including ones embedded deep within the Swiss mountains. Last year, Quartz got an inside look at one of them. Xapo's head of security, Carlos Rienzi, described the situation as being "under attack 24/7. This is not a race. It is a chess game. You have to think about the opponent’s next movement. You can never relax.”