Gates spends most of his time at his 66,000-square-foot mansion in Medina, Washington. It took Gates seven years and $63 million to build this behemoth of a house, which is filled with lots of high-tech features. He purchased the lot for $2 million in 1988, but it's now worth an estimated $123 million.
Inside, a high-tech sensor system helps guests monitor a room's climate and lighting. There's also a trampoline room, a 60-foot swimming pool, six kitchens, and a dining hall that can accommodate up to 200 people.
In October 2014, Gates purchased the 228-acre Rancho Paseana for $18 million. The property includes a racetrack, guesthouse, office, veterinarian's suite, orchard, and five barns.
There's a three-quarter-mile dirt racetrack on the property, located in Rancho Santa Fe, California.
Those buildings are filled with equestrian decor. Weight-loss expert Jenny Craig previously owned the property before selling it to Gates.
Gates also owns another horse farm in Wellington, Florida, which he purchased for $8.7 million in 2013. The family's daughter, Jennifer, is an avid equestrian, and they had previously rented the house when in Florida for her competitions.
Gates made headlines last year when it was revealed that he had racked up thousands of dollars in daily fines for placing his "horse-waste storage facility" too close to a nearby pond. It's unclear whether he has resolved the issue with the city of Wellington.
In 2009, Gates reportedly purchased a Wyoming ranch that once belonged to Buffalo Bill Cody. Though the price he paid for the 492-acre property was never reported, it was originally listed for $8.9 million.
Gates has made a number of real estate investments through his personal investment firm, Cascade. That includes a partial ownership of the posh Charles Hotel in Cambridge, Massachusetts.
Source: Wall Street Journal
According to the Wall Street Journal, Gates owns nearly half of the Four Seasons Holding's hotel chain through Cascade, including hotels in Atlanta and Houston. Gates shares 95% ownership with Prince Alwaleed bin Talal of Saudi Arabia.
Source: Wall Street Journal
In 2013, Gates and several unnamed buyers paid $161 million for the Ritz-Carlton in San Francisco. The hotel is now worth $200 million, the Wall Street Journal says.
Source: Wall Street Journal
Cascade has also been linked to the purchase of more than 4,500 acres of farmland in Suwanee County, Florida, near the community of McAlpin. A subsidiary of Cascade paid nearly $28 million for the tract of land.
Source: Tampa Bay Business Journal, Bloomberg