Gunung Mulu National Park, a UNESCO World Heritage Site since 2000, is a 30-minute flight from Miri (MASwings runs daily Twin Otter services). It contains some of the most spectacular cave systems in the world, embedded in 528 square kilometres of dense Borneo rainforest.
The Deer Cave has the largest cave passage on earth — a tunnel so vast that a double-decker bus could drive through with room to spare. Each evening around dusk, three million wrinkle-lipped free-tailed bats spiral out of the cave mouth in a column that can take 20 minutes to pass — one of the great wildlife spectacles in Asia. Sarawak Chamber, accessible by a harder guided caving trip, is so large it is difficult to comprehend; the far wall is invisible in torchlight.
The Pinnacles, a forest of razor-sharp limestone spikes on the flank of Mount Api, require a three-day trek: a boat journey upriver, a 7.8 km jungle hike to Camp 5, then a near-vertical 1.2 km climb using fixed ropes and ladders. The views from the top of the pinnacle zone are extraordinary.
Accommodation at Mulu ranges from comfortable longhouse-style rooms to basic camp beds; book ahead, especially during school holidays.