Danum Valley's survival is partly geographic luck. The nearest town, Lahad Datu, lies 82 kilometers away on roads built primarily for logging trucks. The valley is bowl-shaped, ringed by hills that rise to 1,093 meters, and its interior is accessible only through trails that take researchers and tourists into a canopy so dense that sunlight reaches the forest floor as scattered coins of light. The Danum Valley Field Centre, established for research and education, propagates dipterocarp trees by the hundred thousand - an effort to reforest what has been lost elsewhere. Managed by Yayasan Sabah, the conservation area serves as a living laboratory and has been proposed as a UNESCO World Heritage Site.

Bornean orangutans move through the upper reaches of the forest, building nests in the dipterocarp crowns and descending occasionally to cross gaps between trees. They share the canopy with Mueller's Bornean gibbons, whose calls echo across the valley at dawn. Below them, Horsfield's tarsier - a primate small enough to fit in a human palm, with eyes proportionally larger than any other mammal's - hunts insects in the dark. On the forest floor, the rare Bornean pygmy elephant passes through on migrations that few researchers have fully documented. Sun bears strip bark from trees to reach grubs. Clouded leopards hunt almost entirely at night. The Bornean rhinoceros was present until 2014, when the last known individual was captured and moved to a breeding facility after decades of population decline. Danum Valley is also the only place on Earth where the spectacled flowerpecker has been recorded.

In 2019, researchers discovered a yellow meranti tree in the valley that measured 97.58 meters from average ground level - the tallest tropical tree ever recorded. They named it Menara, which means 'tower' in Malay. The tree was scanned with terrestrial laser technology and drones, then climbed by Unding Jami and his team, who confirmed its height with a tape measure. Menara is the second-tallest flowering plant in the world, shorter only than the Centurion, a Eucalyptus regnans in Tasmania that reaches 100.5 meters. The discovery underscored what scientists had long suspected: Borneo's dipterocarp forests, the most species-rich on the planet for this tree family, produce giants. The valley is home to over 15,000 plant species, with 94 percent belonging to the dipterocarp genus.

Danum Valley's research has focused heavily on its insect fauna, but the land snail community may be even more remarkable. At least 61 species have been recorded within a single square kilometer - one of the richest concentrations of land snails anywhere in the world. The richness extends to every layer of the ecosystem: pitcher plants on the forest floor, over 270 bird species in the canopy, and a fungal network beneath the soil that connects dipterocarp roots across hectares. Visitors who come for the orangutans and elephants often leave most impressed by the scale of the small. A night walk at Danum Valley reveals a world of insects, amphibians, and arachnids that outnumbers the charismatic megafauna by orders of magnitude.