But a year ago Sunday, on Nov. 4, 2017, the ultra-luxurious Riyadh hotel — with its marble floors and vast indoor swimming pool — became a gilded prison, when hundreds of Saudi royals, billionaires and senior government officials were detained in an extraordinary power play by the heir to the throne, Crown Prince Mohammed bin Salman.

The involuntary guests were told they had to sign away large chunks of their assets to be released. The detention involved both psychological abuse and — in some cases — torture, current and former U.S. officials say.

The move, described by Saudi authorities as a crackdown on rampant corruption, allowed the crown prince to tighten his grip and sent a shock wave through the kingdom’s elites.

“This was a shakedown operation and a power consolidation operation,” said one former senior U.S. official who was in office at the time.