When you're among the richest billionaires in the world, what do you do with your spare time?

If you're Microsoft  (MSFT - Get Report) co-founder Bill Gates, you drop $80 million on building your own "smart city." Gates and his investing firm Belmont Partners have invested $80 million to start the development of a 25,000 acre community 45 minutes west of downtown Phoenix, Arizona. According to Belmont Partners, 3,800 acres will be devoted to office, commercial and retail space and 470 acres will be divested to public schools. 80,000 residential units will fill the remaining space. 

Belmont Partners has yet to announce when construction will begin.

Are we looking at the city of the future?

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