Mulu Caves In Malaysia is the important cave. Gunung Mulu National Park in Miri, Sarawak, Malaysian Borneo, encompasses an array of caves and karst limestone formations in a mountaininous equatorial rainforest setting. Within Gunung Mulu National Park is the world's biggest natural enclosed space, Sarawak chamber, in Gua Nasib Bagus. It is 700 m long, 396 m wide and at least 70 m high. Other notable caves are Benarat Cavern, Deer Cave, Wind Cave and Clearwater Cave, which exposes parts of a long underground river going through the park.