Sarawak Chamber

Sarawak Chamber is the largest known cave chamber in the world by area and the second largest by volume after the Miao Room in China. It is in Gua Nasib Bagus (Good Luck Cave), which is located in Gunung Mulu National Park, in the Malaysian state of Sarawak on the island of Borneo.
Discovery.
The chamber was discovered by three British cavers, Andy Eavis, Dave Checkley and Tony White, in January 1981 during the Mulu'80 Expedition. The story of how it was discovered is told in the books "Underground Worlds" and "Giant Caves of Borneo".
Later named Sarawak Chamber, it measures long, wide and a maximum of high, and was estimated as three times the size of the Big Room in Carlsbad Caverns National Park, New Mexico, then thought to be the largest underground chamber. Its volume and area were checked by laser scanning in 2011 and were found to be and respectively.
To reach Sarawak Chamber, one must follow a river upstream from the cave entrance. This long passage has a roof up to high, and may require some swimming and a traverse along a ledge. Accompanied visits can be arranged by the national Park.
Geology and formation.
Sarawak Chamber is formed in Melinau Limestone, a reef complex of Upper Eocene to Lower Miocene age. It was formed by karstic solutional processes in addition to the erosion of its sandstone basement. Its exceptional area is thought to be the result of the stability provided by the structure of the rocks in which it lies, dipping strata forming an anticline flank close to a syncline axis.
Fiction.
The feeling of agoraphobia experienced by one of the discoverers is referenced in the novel "House of Leaves" by Mark Z. Danielewski.