We could have made our way up into the rural mountainous northwest of Vietnam, which we had heard from several travelers was a must-do. Instead, we made a decision to head south and make the most of the dry season in the tropics. We arrived in Dong Hoi at 4.34am and it was cold and raining.Apparently there is a large mountain range separating northern rainy Vietnam from tropical southern Vietnam. We were still on the northern side...

The rain helped us to catch up on a few hours sleep after a bumpy train ride, before joining forces with a Czech couple, a Kiwi and a Brazilian to hire a taxi and tailor a day trip out to Phong Nha - Ke Bang National Park.

The major drawcard of this patch of wilderness is the estimated 300 or more limestone caves which ebb and flow beneath the surface. One of the largest of these was only opened up to the public in 2010, so is almost completely void of western tourists. This is sure to change as the destination was published in the last edition of Lonely Planet. Large areas of vegetation had already been cleared, paving the way for the necessary tourist infrastructure.

We visited two caves, the first called Phong Nha. Upon reaching a modest little village called Son Trach, we piled into a wooden boat skippered by a couple of ladies and a cute little kid. Our craft floated past dozens of fisherman up stream towards a steep limestone cliff. To our amazement our boat continued until we squeezed through into a dark narrow tunnel below the towering cliff. A few minutes later this tunnel opened up into a huge dark cave, and eventually an underground beach! With a small spotlight at the front of our boat showing the way, our motors were cut, so the only sounds were of dripping water and the odd squeak of a colony of bats.

The second cave was called Hang Thien Duong, or 'Paradise caves'. This cave is massive, and was somehow only discovered in 2005! It is one of the largest in Vietnam at 34km long, and the small section we were allowed into was up to 100m high and 150m wide. We had to hike a couple of kilometres through the national park to get to the entrance, where the six of us were joined by a really keen, enthusiastic vietnamese guide who didn't speak any English.. As we descended into the earth our jaws dropped! We were led down into a massive underground entrance hall that really was beyond words. The best exclamation we could come up with was 'YOU SHALL NOT PASS!!!'. Maybe just check out our photos.

Apparently around US $5 million has been been invested in developing tourism for this miracle. Sure to be a major tourist attraction over the next few decades, we were comforted by the effort they seemed to be putting in to conserving the natural state of the cave and promoting 'ecotourism'.

After all this excitement, our new friends quickly moved on and we were left to explore the quiet city on our own. We only spent another day here, but were happy to see the beach for the first time since leaving home, and enjoyed some really fresh seafood on a nice family-run floating restaurant!