Gunung Mulu National Park, National park and UNESCO World Heritage Site in Sarawak, Malaysia.

Gunung Mulu National Park is a protected area in Sarawak containing vast limestone formations that hold one of Earth's largest cave systems. The park features several dramatic caves with enormous underground chambers and hidden river passages running deep within the mountain.

Spenser St. John first described Mulu's limestone caverns in 1858, and Charles Hose later failed to climb Mount Mulu. In 1932 the Berawan rhino hunter Tama Nilong guided Edward Shackleton's Oxford University Expedition to the summit, the first successful ascent. The Sarawak government gazetted the national park in 1974, and UNESCO inscribed it in 2000.

The park's indigenous inhabitants are the Orang Ulu; some Penan live in the east, where about 300 people are permitted to hunt pigs and deer in Subsistence Hunting Zones. Artefacts and human remains excavated from the Cave of the Winds, possibly a former burial site, are kept in the Sarawak Museum.

You can explore different parts of the park on foot or by boat, with accommodation options ranging from simple huts to more comfortable lodges. Flights from Mulu Airport connect the park to major cities, making arrival straightforward.

The Sarawak Chamber in Gua Nasib Bagus was found in December 1980 by a British expedition. It measures 600 m long, 435 m wide and 115 m high, ranking first in the world by area but second by volume, after the Miao Room in Guizhou, China.