Gunung Mulu

Declared in 1974, the park came to international scientific attention after the Royal Geographical Society expedition of 1977-78, in which more than 100 scientists spent 15 months exploring its caves and forest, beginning what is known as the Mulu Caves Project, with more than 20 further expeditions since. It contains the Sarawak Chamber, the largest known underground chamber in the world by floor area — big enough to hold several parked jumbo jets — and Deer Cave, out of which between one and three million free-tailed bats pour every evening in a spiral that can take over an hour to complete. It has been a UNESCO World Heritage Site since 2000.