Some background from a Los Angeles Times article and accompanying slide show:
But not long after moving day, Sinatra had a change of heart. A sea change. He met Ava Gardner, the love of his life, and promptly left his wife Nancy, who begrudgingly granted him a divorce. Twin Palms soon became the setting for one of the 20th century's great romances, the amphitheater in which Sinatra and Gardner conducted their operatic affair. "Maybe it's the air, maybe it's the altitude, maybe it's just the place's goddamn karma," Gardner wrote in her 1990 autobiography, "but Frank's establishment in Palm Springs, the only house we really could ever call our own, has seen some pretty amazing occurrences."
Here's the portion of an AMC special called Legendary Hollywood Homes II in which Twin Palms is featured: