We'd all love to own a luxury property worth millions but in some cases, they can prove to be an eye-wateringly expensive undertaking. From costly restorations to dream houses that spend years on the market failing to sell, these real estate monsters sucked up unbelievable sums of money. But were they worth it?

In 2011, celebrity plastic surgeon Raj Kanodia – who calls Kim Kardashian and Jennifer Aniston his clients – built a 34,000-square-foot mansion in Bel Air, Los Angeles at a cost of around £5.5 million ($6.8m), with the aim of selling it to make a huge profit. The property was listed in 2018 for around £146 million ($180m) and while plenty of potential buyers were interested, no one was willing to pay the price. The home has now been on the market for over a year.

The unbelievably luxurious mansion has a Portuguese limestone facade, nine bedrooms, a spa, a 2,000-bottle wine room, three kitchens and a gym designed by celebrity trainer Harley Pasternak, and boasts stunning views of sprawling Los Angeles below, as well as the sea and the mountains. Kanodia flew in plants and trees from his native India to plant the grounds.

The undeniably beautiful glass mansion was never intended to be as big or expensive as it is now, but with several architects adding luxury elements to the plans, costs soon spiralled out of control. Kanodia told CNBC: "In Las Vegas, terms it’s called 'all in. I’m all in times a million." After failing to find a buyer a year on, Kanodia is now offering the mansion for rent at around £1.2 million ($1.5m) a month, and says he would consider sale offers of more than around £98 million ($120m)  – that’s around a £49 million ($60m) price cut. 

As dire as it seems, Kanodia is not alone in his predicament. Following a boom in luxury house building in 2014 and 2015, there are now so many similarly expensive houses on the market that buyers are able to take their pick and drive prices down. Plus the plastic surgeon is sanguine about the future, saying he'll be happy to live in it until the right buyer comes along. 

Interested in a map to the stars? Check out these hot celebrity neighbourhoods

Lynnewood Hall, a 110-room Gilded Age palace just outside Philadelphia, was designed by Horace Trumbauer for tycoon and art collector Peter Arrell Browne Widener between 1897 and 1900. Due to a complex and sad history, it fell into disrepair. The cost of building the property was said to be $8 million (£6.4m), that's around $200 million (£160m) in today's money. Restoration of the hall is likely to cost about $40 million (£32.6m), and the property is now for sale for around $15.5 million (£12.6m).

When Widener died in 1915, his eldest son George Dunton Widener Sr should have inherited the property, but tragedy had struck the family three years earlier. George and his son Harry both lost their lives when the Titanic – in which Widener had been an investor – sank in 1912. George is said to have hosted a lavish dinner party on board, attended by the ship’s captain E.J. Smith, who left early due to the iceberg warnings.

Widener’s only surviving child, Joseph, inherited Lynnewood Hall, but when Joseph died in 1943, neither of his children wanted to take on the responsibility of maintaining the property. The mansion was left abandoned and fell into disrepair. If it weren't for the Titanic, the house could well still be in the Widener family, but in 1948, a developer bought the mansion and its acreage for just £103,000 ($130k).

In 1952, the estate was purchased again, this time by the Faith Theological Seminary, a branch of evangelical Christians. The group bought the house for £152,000 ($192k) and sold many of its valuable assets – including its mantels, walnut panelling and landscape ornaments, which were very rare – and more than 350 acres of land. The house now only covers 33 acres.

Intrigued? Read the full history of Lynnewood Hall - and its tragic connection to the Titanic

A 157-acre mansion at the highest peak in Beverly Hills, California, which towers over Los Angeles, finally sold in August 2019 after years on the market. Dubbed 'The Mountain', the property eventually sold to its lender, the Mark Hughes Trust, for around just £81,000 ($100,000). It was originally listed for around £800 million ($1 billion).

The property’s asking price was chopped by around £280 million ($350m) in February 2019, bringing it down to around £530 million ($650m), according to real estate news site The Real Deal. Even with the drastically slashed price tag, it was still the most expensive listing in Los Angeles County. Court filings show there is still around £160 million ($200m) worth of debt on the property, partly because of late fees and interest, according to the Wall Street Journal.

The property has bounced around the market for decades, but there were many potential deals that were abandoned, according to the Wall Street Journal – sources revealed that Tom Cruise put down a deposit for it in the mid-2000s, and that Amazon’s Jeff Bezos recently looked to invest in the property but thought it was too expensive.

The property is big enough to fit both the Disneyland and Disney California Adventure theme parks, with 1.5 million square feet of land ready to be built on – enough room for a football pitch, amphitheatre, helipad, and a polo field side-by-side. The mansion is said to be so high that no nearby trees block the sprawling view of Los Angeles below.

Love this? Then check out America’s most amazing estates that money can buy

When an arsonist threw a Molotov cocktail onto the front porch of The Texas Governor’s Mansion, Austin, in June 2008, the property was almost destroyed. Officials say that if it had been burning for 10 more minutes, the historic landmark – the oldest of its kind west of the Mississippi – would probably no longer be standing. After the fire, a huge restoration project got underway, and cost around £20 million in total ($25m). The arsonist’s identity still isn’t known 11 years later.

Most of the Greek Revival structure survived the fire, though the roof and front windows were destroyed. So much water was used to fight the blaze that it completely filled the basement and left eight inches of standing water inside the mansion, but once it dried, workers discovered that most of the expert millwork and craftsmanship had survived.

The old white brick fence around the property, erected as a security measure after then-Governor John Connally was shot and wounded in Dallas during the 1963 Kennedy assassination, was replaced with a wrought-iron decorative fence. New eco features were also added to the building – a geothermal heat pump provides air conditioning and heating, and solar collectors on the roof generate hot water.

Rick Perry, who was Governor at the time of the 2008 fire, had already moved out of the mansion temporarily so that it could be upgraded (which, ironically, was to involve the installation of a fire safety system). This meant that artwork, decorations and furnishings – including seventh Governor of Texas Sam Houston’s four-poster bed – had already been removed and weren’t damaged in the blaze.

Ready for more? These are America's most endangered historic houses

The Preservation Society of Newport County urgently needs funding for repairs at six Gilded Age mansions, set to cost around £3.5 million ($4.2m). Newport, Rhode Island was a popular place for the nouveau riche to build holiday homes between 1870 and the early 1900s. Rosecliff, pictured, was commissioned by Theresa Fair Oelrichs in 1899 at a cost of around £2 million ($2.5m). Oelrichs hosted lavish parties here – one even featured Harry Houdini. Now, the mansion's balustrade is deteriorating.

When Marble House was completed in 1892, it set the tone for Newport's transformation from a quiet summer colony of wooden houses to a resort of opulent stone palaces. Now, its roof needs to be restored, which is likely to cost around £1.2 million ($1.5 million) – the Preservation Society has applied for a grant that would partially cover it. While that sounds expensive, the society says that if the roof was to leak, the damage to the mansion's beautiful interior would be even more costly. 

The Elms mansion was conceived in 1898, when Mr and Mrs Edward Julius Berwind commissioned architect Horace Trumbauer to design a summer residence for them, modelled after the mid-18th-century French château d'Asnières. The lead used to build the flat roof at The Elms has since bubbled up, causing damage that is likely to cost upwards of £360,000 ($450,000) to repair. If the Preservation Society is able to secure funding, it plans to restore the roof using new materials.

The Breakers is the grandest of the mansions at Newport. It belonged to the extremely wealthy Vanderbilt family, and its design was inspired by the 16th-century palaces of Genoa and Turin. But its current state is far from its former glory – the property needs windows repaired on the third level, while the serpentine path that winds around the mansion also needs work.

Want to know more? Read the incredible stories behind abandoned American stately homes

The vast Wentworth Woodhouse, just outside Rotherham in the South Yorkshire countryside, was once the largest private residence in Britain. It’s been bought by a charitable trust with the aim of opening it up to the public but now faces a £200 million ($249m) repair bill. If the mansion looks familiar, it may be because it was used as a double for Buckingham Palace in 2017 Churchill biopic Darkest Hour.

The crumbling property was bought for £7 million by the Wentworth Woodhouse Preservation Trust, which believes it could become as well-loved as iconic country houses such as Chatsworth or Blenheim Palace. If it were opened to the public, they would be able to explore an estimated 365 rooms and cupboards the size of an average living room. The mansion’s 606ft facade is wider than that of Buckingham Palace, while its floor area is around the same as that of the Moscow’s Grand Kremlin Palace.

The trust’s chief executive Sarah McLeod told The Sun that she believes that the total repair bill could be between £150 and £200 million and that it will be a long-term project. The trust hopes to raise the huge sums of money needed through a mixture of public grants and private donations.

The trust’s first priority is to fix the mansion’s four-acre leaky roof, a mission that has been funded by a £7.6 million grant from the treasury. Work began on the roof in June 2019 and has involved emergency stone repairs – including removing 19 urns from the edge of the roof, each weighing 600kg (the size of a polar bear!).

Fascinated? Read more about England’s largest stately home rescued from ruin

Jackie Siegel and her family gained notoriety after appearing on the documentary Queen Of Versailles, which chronicled their plans to build the self-proclaimed 'largest home in America'. After a rocky construction journey, their £81 million ($100m) Florida mansion is set to be ready in 2020 – 17 years after the building work originally began.

Jackie and her timeshare mogul husband David Siegel began construction on the mansion known as Versailles in 2004, but it has been halted on a number of occasions due to unforeseen events. Firstly, David’s business was hit by the economic crash in 2008; then, in 2015, their 18-year-old daughter Victoria tragically died. Earlier this year, a fire broke out in one of the property’s elevators – meaning that, unusually, it needed renovation work at the same time as being constructed.

Here, Jackie checks on the mansion's progress with one of her daughters. They've got a lot to look forward to – the home will boast 14 bedrooms, 11 kitchens, 30 bathrooms, a 30-car garage, a bowling alley, an indoor roller-skating rink, five swimming pools, a video arcade, a ballroom, a cinema, a gym and spa, a 20,000-bottle wine cellar and an exotic fish aquarium. On the grounds, there will be two tennis courts, a baseball diamond and a formal garden. 

Jackie plans to host a grand opening fundraiser upon the home’s completion in 2020, in honour of her late daughter Victoria. "We've gotten our strength back emotionally through the healing and we're back on track," she told Click Orlando. "We know our daughter would have wanted us to finish it and do the incredible things with the charity events."

Hungry for more? Take a tour of these mansions on 'Billionaire's rows' around the world

Several years ago, a property came on the market in one of London’s most expensive and salubrious areas that would have brought most home buyers out in a cold sweat. Number 39 Charles Street is a Grade II-listed mansion in the heart of Mayfair, so was put on the market for £50 million in 2014. But there was a catch…

Not for the faint-hearted, the grand old 18th-century townhouse needed at least £20 million spent on refurbishment. The house had stood empty for years and so the interiors were in a sad state of decline. Peter Wetherell, managing director of the upmarket estate agents Wetherell, who was handling the sale, told the Evening Standard: “£50 million is a lot of noughts and bandying out this figure willy nilly needs a lot of thought given to why someone would even wish to spend this much on one.” 

But despite its rundown condition, the 15,000-square-foot house couldn’t help but attract attention from the wealthy billionaires drawn to the irresistible potential of owning a historic property in one of London’s most desirable and exclusive neighbourhoods. “We anticipate a fierce battle by super-rich bidders to snap it up. Once converted it will be one of London’s most outstanding mansions,” said Wetherall.

Despite the top-end price tag, London’s most expensive fixer-upper was actually the property investment golden ticket. The house came with planning permission in place to extend the space to 22,000 square feet, adding a basement level with a spa, and a courtyard garden. Once completed, the house could easily be worth £100 million! 

Love this? Prepare to be wowed by the most expensive mansions in the world!