Heading south from Hanoi to central Vietnam, we opted for an overnight train to maximize our time and value. After freshening up and breakfasting in Dong Hoi, we headed out for the days’ big attraction: Phong Nha Cave in Phong Nha-Ke Bang National Park. 
The great cavern is accessed via the Son River. We boarded two long covered boats at the village of Son Trach. Like every landscape in Vietnam, the boat journey was quite scenic as we motored our way up river. Eventually, the quite wide river disappeared altogether into the gaping maw of Phong Nha. 
The name means “Cave of Teeth” but unfortunately, the entrance stalactites are long gone. But once inside the visitor is transported to a magical realm.
The boat captains cut the engines and paddled or pushed the boats for about a kilometer into the dark heart of the mountains. I’ve been in many caves and always find them interesting. But this one was unique – my cavern experiences never included drifting silently along on an underground river. It was somewhat surreal. Multiple and various sized stalactites hung from the ceiling high overhead like icicles.
Lights illuminated the many bizarre formations: cauliflowers, curtains, sponges, grills, and frozen flows. The local guide kept up a steady stream of commentary on the cave’s formation, history, uses, and “named” features. But I have to admit I checked out early and just let the experience flow over me (pun intended). Eventually he stopped talking and we enjoyed the otherworldly ambiance in near silence – accompanied by only the soft rhythm of the boatman’s paddling.
After 20 or 30 minutes of drifting along, we were dropped at a landing. It was another unique experience to step onto a soft, crunchy sand beach – all inside. Our guide took us on a short, meandering, undulating underground hike to show off more of the cavern's features.
These included an ancient Cham alter and many formations that required lots of imagination and the power of suggestion to see squirrels, angels, turtles, and the obligatory phallus. All standard fare in a cave visit, but always fun. The cave itself tunnels back into the mountains another 35 miles. But we were content to explore only the first few hundred meters or so. Eventually we climbed a last series of stairs to emerge 30-40 feet above the cave’s river mouth where we had entered. Some of us climbed up to a hilltop temple above. The views were great as we gazed back down the lazy track of the river. Clambering back down to another landing, this one in sunshine, we reboarded our boats and motored back downstream to our waiting bus and another huge local lunch arranged by our guide Bon.
