Owner: Roman Abramovich, worth $10.2 billion
Purchase Price: 90 million pounds(about $140 million) in 2011
The Russsian tycoon owns several huge London estates (not pictured), including a Billionaires' Row mansion. Since purchasing, plans to build a subterranean extension that includes a tennis court, health center and auto museum were approved by the city. He also owns a French Riviera chateau and in 2009 spent a record $90 million on a 70-acre estate on St. Bart's.