“India’s richest man, and the fourth-richest man in the world, has eschewed  understatement,” the magazine said reporting Ambani’s plans to move into the 570-foot building, called Antila, this month.

Noting that the home is worth 630 million pounds, or $1 billion, as reported by the Telegraph, Forbes said in its last ranking of world’s most expensive homes in November 2009, The Manor, Candy Spelling’s Beverly Hills mansion, won out at a price tag of $150 million.

New mansions may have come on the market since, “but even given those facts, at $1 billion the Antila outprices any home on the market, anywhere in the world, by an order of magnitude,” it said.

“Given the enormous gap between the Antila’s sale price and the known closing cost of any home sold in recent years, there’s an awfully good chance that this is the most paid for a home, ever,” Forbes said noting the highest price paid for a home in 2010 was somewhere between $47 million and $72 million for Le Belvedere, in Bel Air.

According to reports, the “awfully strange-looking tower” has a health club, gym, dance studio, a ballroom, guestrooms, numerous lounges, a 50-seat screening room, an elevated garden, three helipads, and underground parking for 160 vehicles.

The Indian building is a skyscraper, which is bound to fetch more than a single-family home - even a stately 19,500-square-foot building across the street from the Metropolitan Museum of Art such as Helu’s, Forbes said. “But Ambani is moving in with his wife, three children and a modest 600-person staff. That makes it a residence, and by my count, the world’s most expensive,” it said.