Michael Phelps: ~ $2.5 million, Scottsdale
Michael Phelps has long gone into his hard-earned retirement after winning multiple gold medals in the Olympics for many years. And he chose to call landlocked Scottsdale, home. Of course, the fastest swimmer on earth cannot be away from water for long, so his amazing pool is the central fixture of the estate. The rest of the property is not too shabby either with a large five-bedroom main house, barbecue area, and hot tub.