Within the boundaries of Gunung Mulu National Park in Sarawak is one of the most extensive and spectacular limestone cave systems on earth, as well as the second highest mountain peak in the state. Gunung also enjoys unusually high rainfall. As a result it bursts with life, and many new plant and animal species have been discovered here. Officially constituted in 1974 and opened to the public in 1985, Gunung Mulu National Park encompasses only 544 sq. km in North Sarawak, Borneo. Gunung Mulu's Caves are extraordinary. Mulu's Sarawak Chamber is the largest natural chamber in the world, and Deer Cave is the largest cave passage known to man. It has two huge entrances at either end of the mountain it penetrates. Most of Deer Cave is illuminated, one can see 600-foot waterfalls pouring from the roof following a rain storm. Perhaps the most popular attraction of this cavern, however, is the daily exodus of its colony of nearly a million bats. Every evening the bats stream from the cave to spend the night dining on Gunung's rich insect population. Clearwater Cave is the longest cave system in Southeast Asia. Although little of it is open to park visitors without special permission, over a hundred kilometers of passages have been discovered so far. Not all of Mulu's limestone features are contained in caves. Gunung API, a 1,750 meter high mountain of limestone, lies directly beside Sarawak's second highest mountain peak, Gunung Mulu (2,376 meters). Both mountains are over five million years old. About two-thirds of the way up Gunung API sits a mass of enormous razor-sharp limestone pinnacles, the result of the steadily heavy rainfall experienced in this area over the last, oh, couple of million years or so.