Opening Scene is Probably Best Part (wonder where)

OK, I saw Treasure of the Four Crowns in theater at 14 years old. Those were magic years for films in theaters. As a result, it had a magical effect, and imprinted on me. Yes, I'm well aware, it's quite bad in many (many) ways. But once you're imprinted, it's done. Finally having the bluray come out, and seeing an actual CANNON film in widescreen, blew my mind.
My favorite part of whole film (I usually bail right after it's over), is the opening quest at the "castle". I have to say one thing up front. & sorry Tony Anthony... but if they didn't get ENNIO MORRICONE to score this, film would have been a fail. That score 100% saved it (waited years for score to come out too). Speaking of widescreen, there's a scene in that opening, when Striker's about to blow the lid off the coffin. He's stepped off, found cover, and looks over at "something" and sort of scoffs. 4:3 tells you nothing, but widescreen, you can actually see the dead knight (or king) he's looking at.
QUESTION: Where was this castle? Positive the inside was set, but exterior? Would love to know here. Would love a "MAKING OF" book on this.