(OPTIONAL) Paradise cave - the longest dry cave in Asia. Surrounded by forested karst peaks, this staggering cave system extends for 31km, though most people only visit the first kilometre. The scale is breathtaking, as wooden staircases plunge into a cathedral-like space with vast alien-looking stalagmites and stalactites. Get here early to beat the crowds, as during peak times (early afternoon) tour guides shepherd groups using megaphones. From the buggie drop-off, it's a further 600m-plus sweaty climb up to the cave entrance. To explore deep inside the cave beyond the barrier at the end and with luck see the eyeless cave fish that are part of its ecosystem. If you want to do this activity, the tour guide will help you buy the ticket and you pay for that (ticket fee is 270,000 VND or 11 USD per person).

12:30 Enjoy lunch at a local restaurant in Phong Nha village

(OPTIONAL) Explore the most impressive Phong Nha cave. You will take a boat to cruise on Son river about 25 minute to the Phong Nha cave. While on the boat you will see the greenfield, people, houses and limestone along the river. This cave is famous for its rock formation which has been given names such as the “Lion”, the “Fairy Caves”, the “Royal Court”, and the “Buddha”. As the boats reach the caves they queue up, entering only one or two at a time. Engines die and the operators drag them along with long poles, slowly and methodically spearing them into the murky water. Once past the entrance, the immense cavern opens up. Giant stalactite chandeliers hang down from the ceiling. Without prodding or asking, everyone falls silent as eyes gaze up and the stone cathedral’s grandeur spills out. It’s a spectacular sight. If you want to do this activity, the tour guide will help you buy the ticket and you pay for that (ticket fee is 150,000 VND or 6 USD per person).