24 Hour Fitness founder and CEO Mark Mastrov is selling his Lafayette mansion for $13.5 million, reports Realtor.com.

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The 8,000-square-foot estate in Happy Valley offers extravagant indoor-outdoor living. An expansive great room with an aquarium and vanishing walls opens into a sprawling pool area. Outside are two spas, waterfalls and a rooftop firepit. Fitness buffs also won’t be disappointed with a gym, massage room as well as a tennis court, batting cage, putting green and basketball area.

Anton Danilovich and Herman Chan with Golden Gate Sotheby’s International are the listing agents.

Mastrov was born in Oakland and attended Castro Valley High School as well as Cal State Hayward. He founded 24 Hour Fitness in 1983 and in 2013 became part owner of the Sacramento Kings.