For decades, Switzerland had a reputation for bank secrecy that made it the most sought after tax haven for billionaires from around the globe. But, after more than 80 years of secrecy, a series of bilateral agreements with countries around the world, including America’s Foreign Account Tax Compliance Act (FATCA), have forced the private-banking industry in Switzerland to embrace an entirely new era of transparency that requires a full exchange of tax-relevant information with more than a hundred countries.

Which, as Bloomberg points out, has been a huge boon for Swiss operators of private vaults which are not subject to the same transparency and reporting requirements as banks. In fact, these super-secret, privately operated storage facilities buried around the Swiss Alps can basically store anything from anybody because they're not even required to report suspicious activity to Switzerland's Money Laundering Reporting Office.

“There is growth in gold,” Wipfli says. “Since 2008 there has been a real interest in alternatives to bank deposits.” The company explicitly taps into that demand. Swiss Data Safe “is independent from the banking system and any other organization or interest group,” according to a PowerPoint presentation Wipfli shows clients. The company and its anonymous rival aren’t regulated by the Swiss financial-services regulator Finma. Nor do such companies have to report suspicious activity to Switzerland’s Money Laundering Reporting Office. In the past, submissions to the agency have led the Swiss attorney general to open investigations into corruption at FIFA, the global soccer body, and banking ties to Brazil’s Petrobras bribery scandal.

Moreover, American citizens aren’t required under FATCA to declare gold stored outside of financial institutions either. So perhaps it's no surprise that, according to the Swiss defense department, of the roughly 1,000 former military bunkers still in existence across Switzerland, several hundred of them have been sold to private individuals who are now operating them as private storage sites for the gold stash of the world's wealthiest of billionaires.

“The gold trade is a huge part of the Swiss economy,” says John Cassara, a former U.S. Treasury special agent and the author of books on money laundering. “I’m not surprised that there are not more effective efforts in Switzerland to better monitor its misuse. The powers that be don’t want to crack down.” In the first half of this year, 1,357 metric tons of gold—worth about $40 billion—were imported into Switzerland, according to the Swiss customs office, putting the year on course to be the biggest since a record in 2013.

And, of course, when you're storing billions of dollars worth of gold bars, secrecy is a must. As one unanimous vault operator told Bloomberg, his vault sits adjacent a private landing strip which allows quick access to his former military bunker buried in the granite face a mountain deep in the Swiss Alps.

Deep in the Swiss Alps, next to an old airstrip suitable for landing Gulfstream and Falcon jets, is a vast bunker that holds what may be one of the world’s largest stashes of gold. The entrance, protected by a guard in a bulletproof vest, is a small metal door set into a granite mountain face at the end of a narrow country lane. Behind two farther doors sits a 3.5-ton metal portal that opens only after a code is entered and an iris scan and a facial-recognition screen are performed. A maze of tunnels once used by Swiss armed forces lies within. The owner of this gold vault wants to remain anonymous for fear of compromising security, and he worries that even disclosing the name of his company might lead thieves his way. He’s quick to dismiss questions about how carefully he vets clients but says many who come to him looking for a safe haven for their assets don’t pass his sniff test. “For every client we take, we turn one or two away,” he says. “We don’t want problems.”

Billionaire Tax Evaders: 1; Internal Revenue Service: 0.