The Penthouses at One Hyde Park
In 2011, Ukranian oligarch Rinat Akhmetov bought the two top floors of one of the towers in One Hyde Park, London, for 140 million pounds or U.S. $214 million [source: Hawkes]. This was the highest price ever paid for a residence in the U.K. The 17,000–square-foot (1,670-square-meter) penthouse apartments overlook London's largest park and contain every luxury imaginable, from private gyms to his-and-her studies, and are reserved for the wealthiest of the wealthy [source: Barrionuevo]. There are just 86 units in this ultra-exclusive London real estate development. The "smaller" units in the development went on sale in 2007 for $20 million apiece. Despite shelling out all that cash, the apartments are apparently not luxurious enough. Akhmetov's spokesman confirmed that he would spend an additional $90 million on renovations [source: Barrionuevo].
But you don't just get a fancy address when you buy into One Hyde Park. Residents are protected by watchmen from the British SAS (Special Forces) and security features such as bullet-proof windows and iris scanners are the norm [source: The Telegraph]. The building itself has emergency exits leading to an underground tunnel to the nearby Mandarin Oriental Hotel, but the penthouse's residents could simply run to their panic rooms if something happens. During less stressful times, One Hyde Park dwellers can bathe in communal spas, play on the squash courts or drink wine in tasting rooms [source: Teather]. If you don't feel like cooking, the penthouses include 24-hour room service form the Mandarin Oriental Hotel [source: Moore].
London has one of the hottest housing markets in the world, including the Hyde Park mansion that comes in at number two on our list.