Museums.
In Arab cultures if a person compliments an item, you're suppose to give them the item. If Trump said, "that's a beautiful sword", or yacht, or ring - whatever - the Sauds would be duty bound to insist he accept the item as a gift.
I remember when Trump said in his speech something about the 'magnificent' room - I feared the House of Saud would rip the room from the ground and ship it to DC. I was thankful when that didn't happen. Let's pray our President - a good man - didn't compliment them on these items - these treasures.