Net Worth: $40 billion
Gates’ 66,000-square-foot compound is built into a hillside on the edge of Lake Washington, near Seattle. Out-of-shape visitors can skip the 84-step hike to the ground floor and opt for an elevator ride instead. Among its enviable amenities: a 60-foot swimming pool with an underwater music system, a 2,500-square-foot gym and a 1,000-square-foot dining room, which seats 24.
Net Worth: $19.3 billion
In 2004, Mittal paid $128 million for this 12-bedroom townhouse in the luxe Kensington neighborhood called Billionaires’ Row. Mittal’s mansion, tucked between Kensington Palace and the Sultan of Brunei’s spread, has an indoor pool, Turkish baths and garage space for 20 cars. The super-home is embellished with marble taken from the same quarry that supplied the Taj Mahal.
Net Worth: $22.5 billion
Over the last few years, the Oracle co-founder has kept jaws a-dropping by spending $200 million by some estimates on near a dozen properties in Malibu, including five homes that in aggregate would create a custom compound. His 23-acre estate in Woodside, pictured here, is reminiscent of a 16th-century imperial Japanese palace and reportedly cost upward of $100 million to build.