These mansions are not what they seem, hiding secrets from a massive underground spa to a covert man cave buried under the front lawn. Take a look inside four homes with incredible subterranean lairs that you have to see to believe.
Subterranean secrets in St. Moritz
From the outside, this chalet in St. Moritz, Switzerland looks like a relatively modest one-story home. But in reality, it's a behemoth with seven levels, most of which are hidden underground.
When the home hit the market in 2017, its $185 million price tag made it the most expensive home for sale in Switzerland.
The home's most extraordinary amenity is six levels down by elevator, built into the rock below: a massive subterranean spa.
"This place was built to make a billionaire's jaw drop," said Douglas Elliman/Knight Frank global agent Senada Adzem who represented the seller.
Off the elevator there's a giant pool with a Venetian sculpture suspended above it.
Right next to the pool is a huge candle-lit hot tub.
Steps away from the hot bath is steel-clad ice chamber.
There's also a Himalayan salt room with glowing rock walls.
Adzem says the owner declined two offers and ultimately decided to keep the home.
Moroccan surprise
In Rolling Hills, California is a mansion called "Hacienda de la Paz" that also looks deceivingly small from the outside. But don't let the villa's single-story exterior fool you.
This massive homes spans 51,000 square feet, much of which falls below ground. It took the original owner, food magnate John Blazevich, almost two decades to build the nine-bedroom, 25-bath residence. Community rules restricted him from building above the first level , so he built down...way down.
And if you know where to find it, there's a secret passageway that leads to a mind-blowing subterranean lair more than 20 feet below ground-level.
One of the lower levels includes a 10,000-square-foot Moroccan-themed spa with an authentic Hammam and elaborate archways that lead to a stunning lap pool.
The more than seven-acre estate has another pool in the sun drenched backyard.
On another below-ground level is a tennis court built into a 15,000-square-foot space that was designed to convert into a subterranean ballroom. (If you prefer playing on a clay court, there's one of those out back as well, with views of the Pacific.)
Once listed for $53 million, the mega-home sat on the market for several years with no takers. Blazevitch eventually put it up for auction in 2018 when it sold for a fraction of the asking price, bringing in just $22.4 million.
Covert man cave
The former CEO of Patron Spirits built an extraordinary beach-front mansion in Manalapan, Florida. The 40,000-square-foot home has nine bedrooms, 16 baths and two levels that you can see from outside. But there are more below ground.
What you can't see when you look at the exterior is what's buried under the front lawn.
A doorway off the lower part of the estate's driveway leads to a covert man cave.
The space includes an underground lounge and bar, as you might guess it's stocked with tequila. Next to the bar is where Brown, who is also a race car driver, parked his Ferrari 458 and Le Mans prototype race car. He's also put a racing simulator and giant TV down here.
In 2017 the home was on the market for the $48.9 million. It sold that same year for $40 million.
Hidden in the Hills
From ground-level, this Beverly Hills residence could be mistaken for a one-story modern mansion...
...with a very nice pool out back.
But this seven-bedroom, 11-bath house has whole other world hidden down below.
These steps lead to an underground level where you'll find a glass waterfall that spills into the home's second pool.
And while it's subterranean, it's still open to the sky above, so you can still get a suntan.
Off the pool there's a sleek gym...
...and a spa with plunge pools.
The wellness area includes a hair salon and massage room.
On the other side of the pool, there's a full bar that glows...
...and a fireside lounge.
Right next to the lounge is a tasting room with glass walls filled with bottles of wine.
And if you're up for some subterranean Netflix and chill, there's also a movie theater down here.
Back in 2017 the home hit the market with a whopping $100 million price-tag. It's since been reduced to $79.9 million, it's listed with Williams & Williams Estates Group.
Ray Parisi is senior executive producer of CNBC's special projects unit. CNBC producer Jessi Joseph contributed to this report.
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