The basin sits near the geographic center of Sabah, in the Tongod District of the Sandakan Division. Its defining feature is the rim: a ring of steep cliffs and ridges that encircle the interior like the walls of a natural fortress, rising to Mount Lotung at 1,667 metres. Within the basin, the Maliau River and its tributaries have carved a landscape of waterfalls, lakes, and deep forest valleys. Maliau Falls cascades through the interior, and Lake Linumunsut sits hidden in the lowlands. The geological isolation created by the rim has allowed ecosystems to develop in near-total seclusion, producing a concentration of biodiversity that rivals anywhere on Earth.

In an unusual reversal of the typical conservation story, Maliau Basin was protected before it was fully explored. The Sabah Foundation, known as Yayasan Sabah, designated it a conservation area in 1981. Sixteen years later, in 1997, the Sabah State Assembly gazetted the basin as a Protection Forest Reserve under Class I, the highest level of protection. Efforts are now underway to nominate the area as a World Heritage Site, a recognition that would place Maliau alongside sites like the Danum Valley and Kinabalu Park in the global conservation landscape. The decision to protect first and study later may be Maliau's most important legacy.

In 2011, the Maliau Basin Studies Centre opened, providing researchers with a permanent base for fieldwork in one of the planet's least-disturbed ecosystems. Universities from across the globe have conducted expeditions here. Sheffield University, Griffith University, and Otago University have all sent field course students into the basin, and the citizen-science organization Taxon Expeditions has brought non-specialist volunteers to participate in species discovery. The basin's birdlife is exceptional, with Maliau being one of only a handful of locations where the elusive Bulwer's pheasant has been photographed. Each expedition adds to the catalog of what lives within the rim, and each catalog entry reinforces the argument for the basin's continued protection.

Maliau Basin exists in tension with the world beyond its escarpments. Sabah's economy depends heavily on timber and palm oil, industries that have transformed vast tracts of Borneo's lowland forest into plantations. The basin's protected status has kept it intact, but the contrast between the pristine forest within the rim and the altered landscapes outside grows sharper each decade. From the air, the boundary is visible: an abrupt line where unbroken canopy gives way to the geometric patterns of agricultural development. Maliau Basin is not just a wilderness preserve. It is a baseline, a record of what Borneo's forests looked like before the modern economy arrived, and a reminder of what is lost when they are converted.