The Billion-Dollar Address

Inside the biggest, most expensive private house that has ever existed — a 27-storey vertical city with a snow room, three helipads, and a price tag that keeps climbing.

There is a version of this story where the biggest house in the world and the most expensive house in the world are the same building. That version is tidy, cinematic, and mostly wrong. The truth is messier and, frankly, more interesting: the title splits in two, between a 2,000-foot-plus vertical mansion on a traffic-choked street in South Mumbai and a 1,788-room royal compound on a Bruneian riverbank that most of the planet will never be allowed to photograph up close.^1,2 We went looking for both.

Antilia: A House Shaped Like a Skyscraper

Named for a mythical phantom island that Spanish cartographers once insisted existed somewhere in the Atlantic, Antilia was built between 2006 and 2010 on Altamount Road, a stretch of South Mumbai so expensive it has its own nickname: Billionaires’ Row.¹ Twenty-seven storeys, 173 metres, and roughly 400,000 square feet later, it stands as tall as a conventional 60-storey tower, because almost every ceiling inside is double-height.^1,6 The Chicago firm Perkins & Will handled the architecture; Hirsch Bedner Associates, working out of Los Angeles, did the interiors, after Ambani’s wife Nita reportedly fell for their work on the Mandarin Oriental in New York.¹

What’s Actually Inside

The lower six floors are parking — space for 168 cars, plus a dedicated service floor for keeping them running.⁷ Above that, the house unfolds like a private resort stacked on itself: a 50-seat theatre, a ballroom whose ceiling is roughly 80 percent crystal chandelier, a health centre, a yoga studio, a dance studio, a spa, an ice cream parlour, and — the detail every outlet reaches for first — a snow room, where the walls dispense actual snowflakes to cut the Mumbai heat.^6,7 Three hanging gardens, modeled loosely on Babylon, thread through multiple levels. Nine to ten elevators, each finished differently, move family, staff, and guests along separate paths.^1,7

The top six floors belong to the Ambani family alone. Nita Ambani has said the choice was about sunlight, not distance from staff.⁸ Every floor uses a different material palette — marble, mother-of-pearl, crystal — built around a repeating lotus-and-sun motif, and no two floors share a floor plan.^1,6 Reported art inside includes pieces attributed to M. F. Husain and Pablo Picasso.⁹ Three helipads sit on the roof, though as of the most recent reporting they still lack the civil-aviation and defence-ministry clearances required to actually land a helicopter.¹

“Considered by some to be the tallest single-family house in the world — if you’re willing to count a staff of six hundred as part of the family.”

That staff number is not an exaggeration. Roughly 600 people work the building in shifts, which is precisely why some engineers refuse to call Antilia a single-family home at all.^1,10 The building was engineered to survive a magnitude-8 earthquake, sitting on a three-metre-thick concrete raft foundation, with a deliberately tilted structural core and wind-tunnel-tested stiffness to control sway at that height.¹

The Other Contender: A Palace With 1,788 Rooms

If the question is strictly square footage, Antilia isn’t actually the biggest house standing — it just gets the most headlines. That record belongs to Istana Nurul Iman, the official residence of the Sultan of Brunei, Hassanal Bolkiah, on the banks of the Brunei River outside Bandar Seri Begawan.^3,14 Guinness World Records recognizes it as the largest residential palace on the planet: 2,152,782 square feet, roughly seventeen floors including basement levels, completed in 1984 at a cost estimated between $1.4 and $3 billion depending on the source.^3,14,15

The numbers inside are almost absurd next to Antilia’s. 1,788 rooms, including 257 bathrooms. A throne room. A banquet hall built for 5,000 guests. A mosque that seats 1,500 worshippers. Five swimming pools, 564 chandeliers, 51,000 light bulbs, 44 marble staircases, 18 elevators, and an air-conditioned stable for the royal horses.^3,14,15,16 The garage holds somewhere between 110 and over 1,000 vehicles depending on the count, housing a share of a car collection reportedly worth billions on its own.^14,16 Filipino architect Leandro V. Locsin designed the exterior’s golden domes and vaulted rooflines to echo Malay and Islamic tradition; Dale Keller handled the original interiors, later reworked in part by designer Barbara Allen.¹⁴

Unlike Antilia, which anyone can photograph from the street, Istana Nurul Iman is closed to the public for 362 days a year. It opens only during Hari Raya Aidilfitri, when the Sultan and his family reportedly welcome more than 110,000 visitors over three days, handing out food and money to guests who queue for hours.^14,17

Size vs. Spend, Side by Side

Figures compiled from Wikipedia, Guinness World Records, and press reporting cited in the endnotes below; owners have not published independently audited valuations for either property.^1,3,4,14,15

So Which One Actually Wins?

It depends entirely on what you’re measuring. On raw square footage, Istana Nurul Iman isn’t close — it’s more than five times the size of Antilia. On cost-per-headline and sheer cultural fixation, Antilia wins by a landslide; it’s the one people actually argue about at dinner parties, the one Vanity Fair called the world’s most lavish home, the one that gets cited every time someone needs a shorthand for modern excess.^1,18 Buckingham Palace still tops some 2026 valuation lists at a symbolic $4.9 billion, but as a Crown property rather than a private one, most serious rankings exclude it from a “biggest private house” conversation entirely.⁵ Once you take the palace out of the running, the real contest is between size and spectacle — and depending who you ask, that’s a draw.