A newly built modern palace overlooking Los Angeles has just become the most expensive home listed in the United States. Price tag: $250 million.

CNBC can reveal that the 38,000-square-foot mansion in Bel Air, California, will officially come on the market this week — eclipsing the current record holder, a $195 million mansion in Manalapan, Florida. The home has remained one of the best-kept secrets in real estate, since only a handful of billionaires and a few celebrities and top brokers have seen it.