The U.S. commercial real estate market is ripe for a meltdown, according to activist investor and notorious corporate raider Carl Icahn. And he’s putting a lot of money where his mouth is.

“You’re going to have this blow up, too, and nobody’s even looking at it,” Icahn said on CNBC. The investor revealed that he’s shorting the commercial mortgage bond market, noting that it was his “biggest position by far.”

Icahn, who Forbes estimates is worth $15 billion, is focusing his bet on credit default swaps on assets that back mortgages of corporate offices and malls. He made note of the housing market bubble of 2008 and the subsequent collapse of that market, and said he was seeing similar signs now.

“You have a bunch of mortgages … so the banks went out and loaned money against a lot of shopping malls, office buildings, hotels and retail,” Icahn said. “It’s all credible institutions doing it again.”

In its simplest form, a short is a bet that a company’s stock price will be worth less in the future. The short investor borrows stock when it’s high and then sells it when the stock drops – the difference between the two prices is all profit. The practice was immortalized in pop culture after Michael Lewis’ book “The Big Short,” which later became a film. (Steve Eisman, a trader who was the inspiration for one of the main characters in the film, declared in July that his next major short target is Zillow.)

Icahn predicted that mall and other commercial real estate operators would soon default on those loans. And then, freefall.

“It’s like selling insurance to someone who’s going to go to the electric chair in a couple of months,” he said. [CNBC] — TRD Staff