I regret taking a tour for this. You pick one of the activities and spend most of the day on a bus from Hue and back on the same day, and Hue being a WHS makes this an easy follow-up but what I really recommend is staying in the park for 1 or 2 nights and do more than one activity. Don't just "tick" this one off for the sake of completing a list.

I chose the Paradise Cave because it was recommend to be the most beautiful one. It is a big cave and rather impressive for someone who has seen even a few around the world, but was it worth coming all the way for? I ended up chatting with the people on the tour most of the time and we all felt the cave was okay but the guide did not even explain anything to us. There are other caves to explore, zip lining might not be your thing, nor is mud cave exploring (i.e. a bath!), boat trips, and then there is still the forest which is inside the ancient karst region. Having just spent a few minutes at the tourist information booth where some people were dropped off to stay at a local accommodation, I knew there is a lot more to do here instantly.