Sabah

The stunning sapphire waters and emerald isles of the Semporna Archipelago, home to Bajau sea gypsies in Crayola-coloured boats, are plucked from your most vivid dreams of tropical paradise. Of course few visitors come this way for the islands – rather, it is the ocean and the lure of what lies beneath its surface. This is first and foremost a diving destination – one of the best in the world.

Gunung Kinabalu, as it is known in Malay, is the highest mountain on the world's third-largest island. It is also the highest point between the Himalayas and New Guinea. Rising almost twice as high as its Crocker Range neighbours, and culminating in a crown of wild granite spires, it is a sight to behold. March to August (dry season) is considered to be the best time to climb.

The 4095m Mt Kinabalu may not be a Himalayan sky-poker, but Malaysia's first Unesco World Heritage Site is a major drawcard, attracting thousands of climbers every year. The climb, by no means an easy jaunt, is essentially a long walk up a very steep hill, through jungle then barren moonscapes, with a little scrambling thrown in for good measure. On a clear day you can see the Philippines from the summit; often, though, the mountain is wreathed in cloud.

Covering 555 sq km, the Deramakot Forest Reserve has been a success story of sustainable logging, with the strategic felling of tropical hardwoods coexisting alongside conservation efforts that protect some of Borneo's most vulnerable animal species. The reserve has been open to the public since 2012 and has gained in popularity. Around 260 bird species and numerous mammals call this dense lowland forest home, including the rhinoceros hornbill, fluffy crested hornbill, the shy clouded leopard and all of Borneo's smaller wild cats. In the mornings you might hear the lilting call of the gibbon and see sleek simian shapes move through the forest canopy. In the afternoons orangutans rise from their naps and go foraging, while the cover of darkness brings out sambar deer and diminutive mouse deer, civets, giant flying squirrels, wild boars, leopard cats, clouded leopards and bats. Given the reserve's limited visitor capacity, you'll never encounter crowds.

The Kinabatangan River is Sabah's longest: 560km of chocolatey-brown water, coiling like the serpents that swim its length far into the Bornean interior. Riverine forest creeps alongside the water, swarming with wildlife that is being squeezed for habitat by the ever-encroaching palm-oil plantations. Lodges are tastefully scattered along the banks, while homestay programs feature in several villages.

Dozens of boats putter along the banks offering tourists the opportunity to have a close encounter with a wild friend. This is the only place in Sabah where you can find a concentration of 10 primates, including orangutan, Bornean gibbon, long-tailed and short-tailed macaque, three kinds of leaf monkey, western tarsier, slow loris and proboscis monkey. Add to this eight different kinds of hornbill, herds of pygmy elephants, crocs, wild boars and perhaps – if you're super lucky – a clouded leopard.

This pocket of primeval wilderness tells the same untouched story it did millennia ago. Encircled by insurmountable cliffs in southwestern Sabah, the Maliau Basin Conservation Area (MBCA), known very appropriately as 'Sabah's Lost World', is something special.

The basin, a 25km-wide bowl-shaped depression of rainforest, was unnoticed by the world until a pilot almost crashed into the walls that hem it off in 1947, and is the single best place in Borneo to experience old-growth tropical rainforest. More than that, it is one of the world's great reserves of biodiversity, a dense knot of almost unbelievable genetic richness – more than 2000 types of fauna and flora are found here, with more awaiting discovery. It wasn't until 1988 that an expedition into the basin found a self-contained ecosystem of 12 types of forest and tremendous waterfalls. Maliau Basin attracts a small number of adventurous, hardy trekkers and naturalists per year.

A visit to the world's most famous place to see orangutans in their natural habitat is all the more compelling thanks to the outdoor nursery for orangutan youngsters in the same complex, and the nearby Sun Bear Conservation Centre and Rainforest Discovery Centre. In addition, the Labuk Bay Proboscis Monkey Sanctuary is only a short drive away.

What makes Sepilok Orangutan Rehabilitation Centre (SORC) work so well as a destination is its organisation, special-needs-friendly paths, transport links and the fact that, with the exception of the Labuk Bay Proboscis Monkey Sanctuary, the other sights here are all within walking distance. There are also some beautiful places to stay on the edge of the jungle.

A two- to three-night adventure encompasses Romol Eco Village, a Murut longhouse homestay; the Pungiton Caves, an extensive cavern system with underground rivers; an eco-camp by Pungiton located on a riverbank; and finally a sweat-inducing climb up Batu Punggul, a 600m limestone outcrop, followed by a rapid shoot downriver all the way to the Kalimantan border in a motorised canoe.

This eucalyptus plantation is actively involved in the conservation of three groups of pygmy elephants (around 80 in total) that roam its 660-sq-km territory. Come here with 1StopBorneo Wildlife and go looking for elephants on an exhilarating drive in the back of a pick-up truck – one in the afternoon and one early in the morning.