With its bubbling mountains all around, and then it's like wham! boom! this incredible tomb. the impact is terrific. it's monumental, it's massive, it's immense — you run out of adjectives — and it's just here on its own. qasr al—farid — the lonely castle. can you imagine if you were a nabatean trader and you'd come up from the south and you'd cross the desert, and you were hungry and you were thirsty, and then with no reference whatsoever, with no internet, with no photographs, with no paintings, with nothing, you suddenly come across this in the middle of the desert. you must have felt that it came from something larger, something bigger, something divine. in the shadow of this towering monument, i'm meeting wedad yaseen, a new generation of local saudi guide. they greet in arabic at 22 metres tall, this is the largest tomb in hegra. but what clues does it give us about the people who built it? ok, so here we are. tell me about qasr al—farid. lihyan, son of kuza,