The Gunung Mulu National Park is a lush tropical jungle with fast-flowing streams and jagged limestone outcrops. It is overlooked-by a 7,798-foot mountain and is rich with spectacular and immense cave, some of the world’s largest.The Gunung Mulu National Park is located close to the southern border of Brunei with Malaysia Sarawak, about 100km east-southeast of the town of Miri and 100km due south of Bandar Seri Begawan, Brunei, is the largest national park in Sarawak.
Much of the Gunung Mulu National Park, which lies along the Sarawak – Brunei border, was unexplored until the Royal Geographic Society and the Sarawak government surveyed it in the late 1970s. The park was not even opened to the public until 1985. Some of the best examples of tropical limestone weathering (karst) in the world can be seen here including enormous razor-sharp pinnacles, deep-cut canyons, and awesome caverns that are home to millions of bats and cave swiftlets (Collocallia sp., genus Aerodramus sometimes used). These caves include the world’s largest underground chamber, Sarawak Chamber in Lubang Nasib Bagus, capable of holding 40 Boeing 747 aircraft; the world’s biggest cave passage, Gua Payau (Deer Cave), which can fit five cathedrals the size of Saint Paul’s in London; and the longest cave in Southeast Asia, Gua Air Jernih (Clearwater Cave). These huge caverns form in the limestone bedrock because fractures in the rock are widely spaced, the limestone is strong, and the torrential rainfall, nearly 20 feet per year, carries away dissolved carbonate and insoluble sediment.
Anywhere else and these huge caverns would collapse. The diversity of life in Mulu is truly incredible—17 vegetation zones from lowland dipterocarp to upper montane forest. There are 3,500 vascular plant species including 1,500 flowering plant species, 10 Nepenthes species (carnivorous pitcher plants), 111 palm species in 20 genera, and 170 orchid species; 81 mammal species including 28 bat species, 12 in Deer Cave; 76 amphibian species; 270 bird species including eight hornbill species; 48 fish species; and 20,000 invertebrate species with 281 species of butterflies and 458 ant species.