I wouldn't be surprised if Castle Kashan was used in movies to establish that medieval location look, but it also was used in Television as well. In a two-part episode of 'The Rockford Files', Castle Kashan served as the home for musician Tim Ritchie (played by Kristoffer Tabori - Whatever happened to him, anyway?).
Tim Ritchie was plagued by palimony problems, bootlegging of his album by the Mob, and one of his friends was missing. Jimbo was called in to investigate and found the friend dead, and that the case was a lot more complicated than he first thought.
"Only Rock 'n' Roll Will Never Die" (Parts 1 & 2) - October 19 + 26th, 1979.
And now the palatial estate is gone.
This doesn't have to mean that Tim Ritchie's similar-looking mansion also burned down in Toobworld. But if it was located in Malibu as well, I think the castle is history.