Gunung Mulu Caves

The Gunung Mulu Caves are a network of limestone caves within Gunung Mulu National Park in Sarawak, Malaysian Borneo, carved into a thick limestone body that was uplifted and then slowly dissolved by underground rivers over millions of years. The park contains Deer Cave, one of the largest known single cave passages in the world by cross-sectional area, and Sarawak Chamber, the largest known underground chamber by floor area, both shaped by the same combination of river dissolution and chamber collapse typical of tropical karst systems. Deer Cave is also home to several million wrinkle-lipped bats, whose nightly mass exodus is one of the park's best-known sights; the park was inscribed as a UNESCO World Heritage Site in 2000 for its karst geomorphology.