Wikipedia's article has a detailed description of the Plex.
"The four core buildings, totaling (47,038 m²), were built for and originally occupied by Silicon Graphics (SGI). (...) Since the buildings are of relatively low height, the complex covers a large area. The interior of the headquarters is furnished with items like shade lamps and giant rubber balls. The lobby contains a piano and a projection of current live Google search queries. The facilities include a gym (Building 40), free laundry rooms (Buildings 40 and 42), two small swimming pools, a sand volleyball court, and eleven cafeterias of diverse selection. Google has also installed replicas of SpaceShipOne and a dinosaur skeleton. In late 2006 and early 2007 the company installed a series of solar panels, capable of producing 1.6 megawatts of electricity. At the time, it was believed to be the largest corporate installation in the United States."
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