Southern California is home to some of the biggest, priciest, and most coveted pieces of real estate that the US has to offer, and these striking trophy properties are increasingly jam-packed with outrageous luxuries, everything from doomsday bunkers to champagne rooms and even their own signature fragrance. But that’s just the tip of the iceberg: In Los Angeles, deep-pocketed homeowners are increasingly burrowing their most prized perks underground and away from prying eyes. 

These so-called “iceberg homes” involve architects and builders turning their attentions to a less visible part of most homes—the basement, with homeowners shelling out big bucks for lavishly finished subterranean living spaces, a trend that Zoltan E Pali, design principal and co-founder of Los Angeles-based architecture studio SPF:A, says originally “emerged in response to increasingly strict zoning and planning regulations.” However, these days, in addition to maximising land use, it’s also about protecting existing above-ground views.

Pali’s firm most notably developed the Orum Residence, a glassy, 18,000-square-foot stunner that rests atop a hill in Bel Air. The abode itself, which starred in Tiffany & Co.’s “About Love” campaign with Jay-Z and Beyoncé, floats two stories above ground and conceals a third-floor underneath, complete with a home theatre, gym, spa, cedar sauna, service kitchen, and a 1,000-bottle wine room. This level also connects to an attached guesthouse with four bedrooms, four baths, a kitchenette, and garage. Pali’s company also designed The Bronze House in the Bird Streets area of Los Angeles. Here, the basement level is kitted out with a fitness room, a spa, four guest bedrooms, and a kitchen.

“There has been a noticeable rise in demand for iceberg homes, and I believe their popularity will continue to grow in the coming years,” Pali tells Robb Report. “The ability to create expansive spaces that are hidden from view allows homeowners to enjoy their amenities without drawing attention, which is particularly appealing in celebrity-dense areas like Los Angeles.”

This trend has travelled across the pond as well. For example, Hastings House, an US$18.2 million (HK$141.4 million) former church in London’s affluent Knightsbridge neighbourhood, sports a subterranean swimming pool. Over in the city’s posh Belgravia enclave, Cara Delevingne’s childhood home, which hit the market in May for US$30 million (HK$233.1 million), hides an underground movie theatre, a bespoke cocktail bar, a gym, and a catering kitchen.

It’s worth noting though that these types of spaces come with a set of challenges when it comes to construction, in addition to the time and cost of building and maintenance. Luxury developers estimated that projects of this scale and degree of difficulty in Los Angeles can come with price tags in excess of US$1 million (HK$7.77 million), Fortune reported. But if you can afford it, Pali believes it presents “a unique opportunity for design innovation.”