Mulu - Natural Formations

The Gunung Mulu National Park is situated close to the southern border of Brunei with Malaysia, about 100km east-southeast of the town of Miri and 100km due south of Bandar Seri Begawan, Brunei. It lies between the headwaters of the Tutuh River, a tributary of the Baram River and covers 544km2, ranging in elevation from 50 meters to 2,376 meters. The park is important for its high biodiversity and unique karst (limestone) features. Besides that, it contains seventeen vegetation zones, exhibiting some 3,500 species of vascular plants. It was first constituted on 3 October 1974 but only opened to public in 1985.

The climate here is determined by the Indo-Australian monsoon system. From December to March, it will encounter the wet northeast monsoon and the slightly drier southwest monsoon from May to October. Generally, rainfall is high here with seasonal averages ranging from 4,000 to 5,000mm. Temperatures in the Melinau lowlands range from 23ºC to 26ºC and at Gunung Mulu between 14ºC to 18ºC.

The Park has three mountains, Gunung Mulu 2,376m, Gunung Api 1,750m and Gunung Benarat 1,585m. Many of Mulu’s attractions lie deep below the surface. Hidden right underneath the forested slopes of these mountains is one of the largest limestone cave systems in the world. The Park has a number of world record-breaking caves such as the Sarawak Chamber - largest cave chamber in the world, Deer Cave - largest cave passage and the Clearwater Cave - longest cave in Southeast Asia. There are at least 300km more of explored caves, which provides a spectacular sight. These caves are also home to millions of cave swiftlets and bats.

The oldest of Mulu's caves started to form about 5 million years ago when sideways earth movements resulted in the formation of both limestone and sandstone mountains, lying side by side. Millions of years of heavy rain and the action of rivers and running water carved out the vast subterranean system that exists today. The weathering process still continues; dripping water creates new rock features, limestone is slowly worn away, and underground rivers carve and sculpt the caves, transporting limestone debris to the cave mouth or redistributing it within the system.