Beverly Hillbillies Mansion

You know, I think you're probably correct (although you're incorrect about it being a "rare" instance regarding me). Studying that portion of the film it does look like the Beverly Hillbillies mansion, though to me it doesn't look precisely the same -- which I put down to an unclear memory of the latter, or more properly, looking at the same site in two different venues.

However, what annoys me is that I should have realized that the mansion seen in that shot could not have been in Turkey, for one obvious fact -- so obvious it escaped me. In that nighttime sequence, we see James Mason returning to the "embassy" -- a distance shot of him approaching it, then a close-up of him going through the gate and shutting that.

Now, all of the scenes filmed on location in Turkey were establishing shots, mostly filmed at a distance, of various Turkish sites. This includes all the shots of the characters actually in the locations shown -- except they weren't the cast, but doubles for the actual actors, none of whom went to Turkey. This was all second-unit stuff. You can see that none of the actors is ever seen in close-up while plainly in Turkey; the close-ups are all studio inserts matching the locales seen in the establishing shots. Therefore, Mason could not possibly have been seen -- as he clearly is, even at a distance -- if that sequence had been filmed in Ankara.

So I guess the OP (and you, as usual) were right. But is that also the BH mansion in the scene (at about 1:17) where, after Diello triggers the alarm and runs out, we see Micheal Rennie look out the window and watch him running away through the garden? It looks like Mason's double, not Mason, running away. Of course, they could have employed the double to do the sprint back in Beverly Hills. We don't see the mansion itself in that shot, and while the grounds look similar, from that p.o.v. I can't be certain that it's the same estate (in America).