Cúc Phương National Park

Stop for a moment and listen. The air under the canopy is thick and green, and it carries a damp, earthy smell of leaf litter and wet stone. Somewhere above you, an unseen bird repeats the same three notes. Cicadas rise and fall in waves. The ground underfoot is soft in places and sharp in others, where grey limestone pushes up through the soil. Welcome to Cúc Phương, the oldest national park in Vietnam.

The park was declared in 1962, and that makes it the first of its kind in the country. It came at a time when Vietnam was still young as an independent state and under heavy pressure from war. Setting aside a large tract of forest for protection was an unusual choice in those years. Ho Chi Minh visited the forest in the early 1960s, and his visit is still remembered here as a sign that the young state valued its forests.

The park stretches across a long limestone ridge, and it reaches beyond Ninh Bình into the neighbouring provinces of Hòa Bình and Thanh Hóa. The whole area covers roughly twenty thousand hectares, or about two hundred square kilometres. Most of it is karst country. Karst is a landscape where rain and time dissolve limestone, so the rock becomes full of caves, sinkholes and steep, jagged hills. The same geology shapes the famous river scenery near Ninh Bình, but here the stone is covered in dense forest.

That forest is the real heart of the park. It is tropical evergreen forest, with several layers of plant life stacked on top of each other. Tall trees form the top layer, and climbing vines hang down from them. Below them, smaller trees, ferns and palms fill every gap. Look closely at the base of the big trunks. Many have broad buttress roots that spread out like walls. These roots help the trees stand firm in thin soil on top of rock.

One of the best-known walks leads to a tree that locals call the thousand-year-old tree. It is a giant of the forest, and you will need to tip your head right back to follow the trunk upward. Nobody can give its age with precision, so treat the name as affectionate rather than scientific. Still, standing at its base gives you a real sense of scale. Its roots alone are taller than a child, and the canopy disappears into the leaves of its neighbours.

Here is something many visitors do not expect. These caves were home to people long before the park existed. In one cave, known in English as the Cave of Prehistoric Man, archaeologists found human burials, stone tools and the remains of ancient meals. The finds date back many thousands of years. So when you climb the steps into the cool, shadowed rock, you are walking into a place that people chose for shelter in the deep past.

The forest still has human neighbours today. The Mường people, an ethnic group closely related to the Vietnamese, have lived in these hills for generations. Some Mường villages sit inside or at the edge of the park. Their traditional houses stand on wooden stilts, with space underneath for animals and storage. If you visit a village, you may hear the Mường language and see weaving, rice fields and small gardens set against the limestone walls.

Now for the second surprise. Near the park entrance is a rescue centre for some of the rarest monkeys on Earth. The Endangered Primate Rescue Center was founded in 1993 by the German conservationist Tilo Nadler, with support from the Frankfurt Zoological Society. It cares for langurs, gibbons and lorises that were rescued from hunters and illegal traders. Some of these animals belong to species that live only in Vietnam and nowhere else.

The most famous of them is the Delacour's langur. It is a slender black monkey with a long tail and a broad white patch across its hips and thighs. Many people say it looks as if the monkey is wearing white shorts. It survives only in a small part of northern Vietnam, and it is critically endangered. At the centre you can watch these langurs moving through their enclosures, and you can learn how staff prepare some of them for life back in the wild.

Just nearby is a second centre, this time for turtles. Many turtle species in Vietnam and across Asia have been hunted almost to extinction for food and traditional medicine. This centre breeds and protects them, and it explains the threats in clear, simple displays. It is a quiet place, and it is easy to walk past. But it shows the same idea as the primate centre. The park does not just protect trees. It also gives a refuge to animals pushed out of other places.

The park changes with the seasons. In spring, often around April and May, huge numbers of butterflies appear along the roads and streams. Yellow and white wings gather on damp ground to drink, and they rise in clouds when a car passes. The rainy summer brings heavy, steamy heat and very green leaves. Winter is cooler and drier, and the trails are easier to walk. Each season gives the forest a different sound and a different colour.

As you explore, you may hear more than you see. Most wild animals here are shy, and the forest is very dense. You might catch the call of a hornbill, or the rustle of a squirrel in the branches. Look down as well as up. You may find bright fungi on fallen logs, beetles with metallic shells, or a line of ants crossing the path. In this forest, small details can be as interesting as the giant trees.

Before you leave, stand still once more and let the forest settle around you. Notice the light, broken into small green coins by the leaves. Feel the cooler air that rises from the rock. Listen to the insects, which never quite stop. This forest has been protected for more than sixty years, and the limestone beneath it is far older than that. As you walk back toward the road, watch the trees at the edge of the forest, and notice where the shade ends and the open sky begins.