If you are a high net worth individual you probably already know about it. A seminar on the subject at Manhattan’s Harvard Club attracted financial advisors to some of Americas richest dynasties—including the Pritzker and Soros families.

A Las Vegas meeting on the subject was organized by former White House aide Anthony Scaramucci and attracted such attendees as Mark Cuban, the billionaire owner of the Dallas Mavericks, and former New Jersey governor Chris Christie. It has spurred the Swiss bank UBS to create a fund for its “ultra high net worth” clients—people who have at least $50 million in investable assets.

So, what’s all the excitement about? They are called OZs, or Opportunity Zones. They are the hottest investment opportunity around, and they were created by a mere 8 pages in the 185-page tax reform bill the Republicans passed in 2017.

In theory, the idea was to provide capital to revitalize the urban areas that President Trump has portrayed as “wastelands, ravaged by crime and homelessness and infested by rats.” In practice, it’s gentrification on a grand scale—as luxury high-rises for the rich replace run-down buildings and other structures.