Hearst Castle
I'm surprised Phil/Tandy never went there and swam in the outside pool. I've been there on tour and it's such an epic view from there, entirely something that would happen in the first season of the show.
The minor detail is that it only appears for exactly one second in the original Spartacus and in a Lady Gaga music video G.U.Y.
It must be outrageously expensive to film there since it's only in one movie or they just don't allow it most of the time.