Important both for its high biodiversity and for its karst features, Gunung Mulu National Park, on the island of Borneo in the State of Sarawak (yay Malaysia!), is the most studied tropical karst area in the world. The 52,864-ha park contains seventeen vegetation zones, exhibiting some 3,500 species of vascular plants. Its palm species are exceptionally rich, with 109 species in twenty genera noted. The park is dominated by Gunung Mulu, a 2,377 m-high sandstone pinnacle. At least 295 km of explored caves provide a spectacular sight and are home to millions of cave swiftlets and bats. The Sarawak Chamber, 600 m by 415 m and 80 m high, is the largest known cave chamber in the world.
Gunung Mulu National Park has the largest known natural chamber or room – Sarawak Chamber, found in Gua Nasib Bagus. It is 2,300 feet (700 m) long, 1,300 feet (396 m) wide and at least 230 feet (70 m) high. It has been said that the chamber is so big that it could accommodate about 40 Boeing 747s, without overlapping their wings. The nearby Deer Cave is one of the largest single cave passages in the world, if not the largest.
Other notable caves in this area are Benarat Cavern, Wind Cave, and Clearwater Cave; which contains parts one of the world’s largest underground river systems and is believed to be the largest cave in the world by volume at 30,347,540 m³.
Mulu’s limestones belong to the Melinau Formation and their age is between 17 and 40 million years (Late Eocene to Early Miocene).
Stratigraphically below the limestones, and forming the highest peaks in the south east sector of the Park including Gunung Mulu, lies the Mulu Formation (shales and sandstones). The age of these rocks is between 40 and 90 million years (Late Cretaceous to Late Eocene).
Mulu National Park is a very remote access area; the only practical way of getting to and from it is by air, through Mulu Airport. There are flights between Mulu Airport and Miri (daily), Kuching(Tuesdays, Thursdays and Saturdays) and Kota Kinabalu (Tuesdays, Thursdays and Saturdays) on MASwings. Alternatively, it is possible to travel by river from Miri, which is about 100 km away, using a riverboat, then a chartered long boat, which in total takes around 12 hours. Before the opening of the airport and the opening of a helipad in 1991, this was the only way to reach the national park.
Excursions to Mulu continues to retain the sense of adventure associated with its original exploration through the provision of adventure caving and other adventure activities. The primary focus, however, has shifted to the promotion of an awareness of the significance of the park and its environment through the provision of ecotourism activities that foster understanding and appreciation of the parks values. Accommodation is available onsite at Gunung Mulu National Park headquarters, as well as at the Royal Mulu Resort and across the Melinau River at Benarat Inn also known as Benarat Lodge. Homestays offered by locals, and other typically cheaper lodging are available across the river.