One of my all-time favorites. Most people probably know that Kane is loosely based on William Randolph Hearst.
I read Harpo Marx's autobiography, which has some stuff on his experiences at San Simeon. Like Kane, Hearst had a giant fireplace built that was big enough to hold a truck. In Marx's first visit to San Simeon, he had to sit at the fireplace end of the dinner table. He said he couldn't eat fast enough to make up for the pounds he was sweating off.