Phong Nha lies in central Vietnam in a country made of limestone, a landscape of jagged green peaks, hidden valleys and rivers that vanish underground. The village sits on the Son River, in Quang Binh province, and the nearest big town is Dong Hoi, about forty kilometres to the east on the coast. Behind it, the mountains rise toward the Laotian border, and the whole region was declared a World Heritage Site in 2003 for its caves and karst.
The caves are the reason people come, and there are genuinely extraordinary ones. Son Doong, found in 1991 by a local man and first explored by British cavers in 2009, is thought to be the largest cave passage in the world, big enough to hold a jungle and a skyscraper. Visiting it takes a permit, a guide and several days. Easier to see are Phong Nha Cave, reached by a long boat ride along the river, and Paradise Cave, with its long walkway through huge chambers of stalactites. Nearby, the Bong Lai valley has rice fields and buffalo, with a beautiful, slow feel.
The war left its mark. This area was on the Ho Chi Minh Trail, the supply network that ran through the mountains from north to south during the Vietnam War, and heavy American bombing hit the region. Craters still pock the fields and caves were used as hospitals and storage. Locals sheltered in the caves during the bombing, and old unexploded ordnance is still a hazard away from marked paths, so stay on established trails.
For riders, the Ho Chi Minh Road runs south from here through the mountains of the Central Highlands. It is a modern road built over the old trail, with long, smooth curves, forested slopes and little traffic compared with the coastal highway. Surface quality varies, with landslide patches, potholes and the occasional water buffalo or herd of cattle in the lane, so watch the road ahead. Mist hangs in the valleys in the early morning, and the light is often soft and hazy.
The rainy season, roughly from September to December, brings typhoons and flooding that can cut roads, while the dry season from March to August is hot, with strong sun. Fuel stations are in Dong Hoi and on the main road, but fill up whenever you see one on the mountain sections. Local food is simple and good, with rice noodle soups, grilled pork and the fresh river fish served at small family restaurants.