Ulu Temburong National Park

Listen first. Under the green roof of this forest, the air hums. Cicadas rise and fall in waves, sometimes so loud they sound like machinery. Water drips from leaves long after the rain has stopped. The ground under your boots is soft and dark, a layer of fallen leaves that never quite dries. The light comes down in pieces, green and gold, filtered through layer after layer of leaves. Welcome to Ulu Temburong National Park, in the far eastern part of Brunei.

The name carries a clue. In Malay, the word ulu means the upstream country, the headwaters, the remote interior where rivers begin. So Ulu Temburong is, quite simply, the upper reaches of the Temburong River. For a long time it was a place reached by few outsiders. Even today, there is no road into the heart of the park. The last stretch of the journey still happens on the water, the way it always has.

Here is the first surprise for many visitors. Temburong District is cut off from the rest of Brunei. A strip of Malaysian territory, part of the state of Sarawak, sits between this district and the capital, Bandar Seri Begawan. For generations, people travelled here by fast boat through mangrove channels, or by road through Malaysia with border checks on the way. Then, in 2020, a long bridge opened across Brunei Bay. It now links the district directly with the rest of the country.

Even with the bridge, the forest keeps its distance. Most visitors travel from the small town of Bangar towards the river jetty, and then board a narrow wooden longboat. The boatmen read the river with care. In the dry season the water runs shallow over pebbles, and the crew may jump out to push. After heavy rain, the river turns brown and fast. Either way, you sit low, close to the water, with the forest rising steeply on both banks.

The forest itself is old. This is lowland and hill tropical rainforest, dominated by tall trees called dipterocarps — a family of hardwood giants known for their winged seeds, which spin down like small helicopters. Much of Brunei's interior was never cleared on a large scale, partly because the country's wealth came from oil and gas rather than timber. That choice left this area largely intact. What you are walking through is primary forest, not a plantation and not regrowth.

The park sits inside a much larger protected landscape. It forms part of a wider forest reserve, and Brunei is one of three countries, with Malaysia and Indonesia, that signed up to the Heart of Borneo initiative. That agreement aims to protect a connected block of rainforest across the centre of the island. So the trees around you are not an isolated island of green. They are one edge of a forest that continues for a very long way inland.

Now look up — because the main reason many people come here is above your head. A canopy walkway is strung between metal towers, high above the forest floor. Reaching it means climbing a long series of wooden steps up the hillside, and then climbing the tower itself. It is hard work in the humidity. Your shirt will be wet before you reach the top. But at the top, you stand level with the crowns of the trees, and the forest looks completely different.

From the walkway, the canopy is not a flat green carpet. It is lumpy and uneven, full of individual crowns of different shapes and shades. Some trees push above the rest, standing alone with broad tops. In the early morning, mist often sits in the valleys and lifts slowly as the sun warms the air. The towers can sway slightly in the wind. That movement is normal, and it reminds you how high you are.

Scientists value this forest as much as visitors do. Upstream, the Kuala Belalong Field Studies Centre is run by Universiti Brunei Darussalam. Researchers from around the world have used it as a base to study insects, frogs, plants and the complex life of the canopy. A second surprise: many of the creatures living in these treetops have barely been studied. Some species found in forests like this are still new to science, and researchers continue to describe new ones from Borneo.

Keep your eyes and ears open for wildlife, but be patient. Rainforest animals are often heard long before they are seen. A deep whooshing sound overhead usually means a hornbill is flying past — large birds with heavy, curved bills, and the wingbeats are surprisingly loud. In the morning you may hear gibbons calling, a rising, bubbling song that carries across the valleys. Lizards rest on tree trunks, and butterflies gather on damp sand by the river.

And yes, there are leeches. Small brown leeches wait on leaves and the forest floor, especially after rain. They are harmless, though a bite can bleed for a while because they release a substance that stops blood from clotting. Many guides offer leech socks, long cotton socks pulled up over the trousers. Locals treat them as a minor nuisance, nothing more. Check your ankles from time to time, and try not to let them spoil the walk.

The people of Temburong are part of this story too. The district is home to Malay communities as well as Iban and Murut people, whose families have lived along these rivers for generations. Many boatmen and guides grew up in nearby longhouses and villages. Their knowledge of the river, the plants and the weather is practical and deep. Ask them which plants are used for food or medicine. Their answers often tell you more than any sign board.

After the canopy, many visits end at the river. The water is cool and clear in calm weather, and it feels wonderful after the climb. Small fish may nibble at your feet in the shallows. Sitting on the rocks, you can watch the light move over the water and listen to the forest close in again. This is a good moment to slow down, before the longboat ride back downstream.

So take a last look around you. Notice the roots spreading across the ground like thick ropes, the thin vines climbing towards the light, the shine of wet leaves. Listen to the cicadas once more. As the boat carries you back towards the road and the bridge, the sound will fade behind you. But this forest will keep its slow rhythm here — growing, dripping, calling — long after you have gone.