The Maliau Basin is sometimes called "The Lost World of Sabah". It was discovered in 1947 from the air by a pilot, but it was only in 1988 that a first expedition organised by Yayasan Sabah and WWF Malaysia visited the region.
It is located in south-central Sabah, about 40km north of the Indonesian border at between 116° 40' - 117° 2' and 4° 40' 4° 50' N. In 1997 the Maliau Basin Conservation Area was upgraded by the Sabah state government to a Protection (Class One) Forest Reserve.
The real beauty of Maliau Basin lies largely in the fact that most of its areas are yet to be explored. There are no human inhabitants in the region. Maliau Basin Malaysia is spread over a sprawling area of 390 square kilometers and has a maximum diameter of 25 kilometers. Mt. Lotung, (1900 meters) is the highest point in Maliau Basin.
The Basin represents a single catchment, and is drained by a set of radiating tributaries of the Maliau River, one of which descends a magnificent series of waterfalls, known as Maliau Falls. Numerous smaller waterfalls have also been discovered throughout the Basin. The Maliau River then drains through a gorge out of the southeast of the Basin into the Kuamut River, which in turn feeds into the Kinabatangan, the longest river in Sabah.
Many of the species in Maliau are listed in IUCN's Red Data Bok or are endemic. More than 1,800 plant species have been identified, including 6 species of Nepenthes and 80 orchid species as well as the giant flower Rafflesia tengku-adlinii. Among the 70 registered mammal species, rare species like Sumatran rhinoceros, Clouded Leopard, Proboscis monkey and Malay Bear are found, especially in the area surrounding the basin itself. 261 species of birds have been identified, and more than 30 amphibian species. The insect fauna is largely unknown.