After purchasing Ba Na Hills through Klook and loving it, I decided to choose a Korean guide for Marble Mountains and Linh Ung Pagoda as well. Our local guide spoke Korean exceptionally well, was very kind, and explained everything clearly and engagingly. Although it wasn't originally planned as a private tour for two, we ended up being the only ones because not enough people signed up. It seems like it's generally a small-group tour anyway. We visited Marble Mountains first, specifically the Thuy Son mountain among the five, and it was truly magnificent! However, what was really disappointing was that we couldn't visit Am Phu Cave, which is constantly mentioned and explained on YouTube! They call it 'Hell Cave,' and it's said to have a lot to see. I'm not sure if it's normally not part of the tour (the guide said it wasn't), but it was skipped. Since there were only two of us, the tour finished a bit quickly, and we went straight to Linh Ung Pagoda. That's when I realized we hadn't gone to the cave. If the guide had mentioned it earlier, they could have taken us, but once we moved on to Linh Ung Pagoda, it was too difficult to go back. ㅠㅠ If you're on a small-group tour like ours, I recommend asking if you can visit Am Phu Cave. Other than that, it was wonderful! But that one omission is a big regret. Haha.