At the St. Moritz ski resort in Switzerland sits a lavish, seven-story home, dubbed The Lonsdaleite, or The Ice Palace.
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It was listed on the market for $185 million last fall. Realtor Senada Adzem told CNBC that the home was "designed to make a billionaire's jaw drop."
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You might think this is your average luxury castle built for the everyday billionaire — that is, until you head downstairs...
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...which is where the real extravagance begins. The underground amenities include a home theatre bedecked in red...
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Owners can ski in and out of a private lift to access the powdery slopes of the Swiss Alps.
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...as does a high-tech shower equipped with controls that can change the lighting and color schemes.
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This colossal, luxury, 7.4-acre Spanish Hacienda took 17 years to construct, and five of its six stories are underground.
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The home is the brainchild of John Z. Blazevich, CEO of Viva Food Group, who circumvented zoning codes prohibiting home expansion by building down into the ground.
Source: Forbes
The infamous underground mansion, dubbed Hacienda de la Paz, spans 51,000 square feet and sports nine bedrooms, 25 bathrooms, and a six-car garage.
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One of the estate's two tennis courts is on one of the five underground levels.
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When owners aren't using it for a court, it doubles as a ballroom that can accommodate 350 dinner guests and a dance floor.
Source: Hacienda de la Paz
A Hamam, a traditional Moorish-style bath spa, also sits underground and is one of the site's two pools. The interior is hand-crafted from imported marble and sandstone, and 24-karat gold Venetian tiles line the space.
Source: Hacienda de la Paz
Skipping around the estate is a breeze — elevators take owners from floor to floor...
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...or back into the open air, where the estate's extravagance is just as unparalleled. An outdoor clay court is lined with comfy seating for spectators.
Source: Hacienda de la Paz
...other underground homes were fashioned out of the paranoia of their owners.
Source: Las Vegas Review Journal
Entrepreneur Jerry Henderson and his wife, Mary, built "The Underground House" in 1978 in the midst of the Cold War as a luxury hideaway bomb shelter.
Source: Las Vegas Review Journal
The property sits 26 feet below the surface with two bedrooms, three bathrooms, a six-foot-deep pool, putting green, and a spa.
Source: Las Vegas Review Journal
And though it's protected from the elements above, owners are still afforded sweeping landscape views, thanks to full-sized murals that line the walls.
Source: Las Vegas Review Journal
The Hendersons passed away in the 1980s, leading to the property's eventual foreclosure, before its current owner swept it up and spent more than $1 million renovating it.
Source: Las Vegas Review Journal
The Hendersons paid around $10 million in constructing the home in the late 1970s. That's about $40 million in today's money.
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For a long time the property remained a bit of a mystery to its neighbors. But the owner recently opened it to the public during a gala.
Source: Las Vegas Review Journal
On the other side of the country sits another luxurious subsurface bomb shelter in Kansas as part of a project dubbed Survival Condo.
Source: Business Insider
The $20 million property spans 15 floors underground and is housed inside an old missile silo. The silo, like Las Vegas' Underground House, was built in the midst of the Cold War.
Source: Business Insider
The project offers up 12 single-family homes to homeowners wishing for a surefire way of preparing for potential catastrophic events.
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A full-floor unit spans 1,820 square feet and can fit six to 10 people. Buyers shell out $3 million for one, which includes three bedrooms, two bathrooms, a kitchen, a dining room, and a great room.
Source: Business Insider
In place of a natural views, the windows are outfitted with screens that show live footage of the landscape outside.
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And if staying fit with gym equipment isn't your forte, there's also a rock climbing wall.
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Family pets are also invited — there's a park in the compound for dog walks.
Source: Business Insider