Beyond the bustling Malaysian mainland, ensconced in the intriguing equatorial rainforests of Borneo, are some of the most expansive caves in the world. The elaborate cave network lies within Malaysia’s UNESCO World Heritage Site, Gunung Mulu, Sarawak’s largest national park. The sandstone mountain of Mulu and its limestone karsts, rock pinnacles, cliffs and gorges belong to the Melinau formation, aged between 17 and 40 million years. This remote access area can be reached by daily flights from Kuala Lumpur via Miri, Kuching and Kota Kinabalu. Till recently, the only ways to travel were by riverboat from Miri and then by longboat from Kuala Baram, or hiking through the ancient ‘Head Hunter’s Trail’ from Limbang. Sparsely populated and covered by a thick forest, Mulu is an explorer’s paradise. It has limited mobile connectivity and no banks. In case provisions run out, there is hardly anywhere to purchase these. Kiosks and eateries sell Malay food in some areas. A medical clinic aids the sick, but helicopters airlift seriously ill patients.

Besides the four show caves (Wind, Clearwater, Langs and Deer), there are the Mulu summit climb, the Pinnacles trail, the world’s longest tree-based canopy walk (480m), the Penan burial cave, other caves and an amphitheatre-like bat observatory. The largest natural chamber, Sarawak Chamber, in the Nasib Bagus Cave is big enough to house 40 Boeing 747s, without crowding. The caves are teemed with insects, snakes, lizards, tree frogs and butterflies. Although difficult to spot, the impenetrable forests are home to bearded pigs, macaques, gibbons, Borneo tarsiers, deer and Malaysian sun bears. A two-to -three night trip is good for the time-starved traveller who can lodge in the stilt-propped bungalows of Mulu Marriott Resort or Benarat Inn along the scenic Melinau River. Locals offer cheaper homestay facilities.

Tours can be booked at the park office. Advance bookings may be needed for the comparatively drier months of June to September, the peak season. Hiring a park guide is compulsory. Recently, a backpacker avoided hiring one to cut costs, got lost and was found in near-death conditions 12 days later.

Torches, raincoats, water bottles, trekking shoes, hats and Malaysian Ringgits are mandatory. Tour itineraries usually include snacks and lunches. Raised wooden planks throughout the hiking path, concrete steps and sensor lights in the caves make the long treks easier for tourists of all ages. As trees canopy most of the trail, the sunrays are partly blocked. However, high humidity can sap energy. To avoid crowding, the show caves are not open all day. The Wind and Clearwater caves are toured in the mornings, and the Langs and Deer caves in the afternoons. The four caves can be covered in one day or over two days. The gates close at specified hours. Gatekeepers count footfall, and to-date no one has had to spend the night in the caves.

The morning tour (8:30am) is along the Melinau River in a longboat, with a halt at the Batu Bangan village of the nomadic and eco-friendly Penans. The gentle Penans are the last remaining hunters and gatherers of Borneo. After World War II, missionaries have tried to settle them. They hunt with ‘kelepud’ (blowpipe) made of wood from Belian trees that can carry darts accurately over 3 metres. The poisonous, latex-tipped darts are made of sago palm. The longhouse market sells handicrafts like uniquely designed handbags, charms, wooden ladles and blowpipes. The market is closed on Sundays. That is the entire shopping that Mulu offers.

WIND CAVE
Over millions of years, water draining along the slopes of Gunung Mulu has cut deep gorges through its limestone rocks and formed intricate networks of caves. The water continually scallops the walls and changes the dimensions of the caves. The Wind Cave is one of many. As the gentle breeze blows through the magical chambers of this cave, an imaginative mind finds resemblances to camels, birds, hands and Chinese gods among the stalagmites, stalactites and helictites. Touching these is strictly prohibited. Nature’s work in progress is often evident, with water dripping from the stalactites on to the stalagmites. The roof and the floor sometimes touch each other to form mammoth pillars, as in the King’s Chamber, a cavern with massive stones. The entrances and skylights ensure a steady stream of wind. This cave forms the southernmost entrance to the Clearwater Cave.

CLEARWATER CAVE
From the Wind Cave to the Clearwater Cave is a 250-step walk or a 5-minute boat ride. It is the longest interconnected cave system in the world by volume and the 8th longest (222km) cave in the world. Uncommon single-leafed pendulum plants welcome tourists at the entrance. The icy and crystal-clear waters of the mighty Clearwater River travel a subterranean route for over 170km, and emerge from a dense forest-covered cliff-face. The ‘measureless’ caverns and ‘dancing rocks’ of Coleridge’s Kubla Khan come to mind. Swimming is not permitted inside the cave. There is a  sandy, refreshing swimming area just outside it, with a perfect picnic spot under giant trees. The afternoon tour (2pm) coincides with the bat exodus at dusk. A 3km wooden walkway with tropical shade, swamps and gurgling streams guide the traveller to the Langs and Deer caves. Caterpillars and millipedes often use the wooden railing as their walkway. Bats and swiftlets are common to both caves.

LANGS CAVE
Named after its discoverer, Langs Cave is the smallest of the caverns, with decorative long shawls, rim-stone pools, stalactites and stalagmites. Shimmering webs spun by the threadworm larvae near the roofs are fascinating. Snakes also take shelter in the niches of the roof.

DEER CAVE
A 100m away is the Deer Cave, with the world’s largest cave passage. It derives its name from the sambar deer that ventures in to lick salt-bearing rocks. The main entrance to the cave is 146m wide. This impressive cave is 4km long, 174m wide and the vaulting dome is 90-122m high. A peculiar rock formation near the entrance, resembling the profile of Abraham Lincoln, and an opening similar to a bear attract attention. The once-raging river that had moved huge boulders is now a noisy trickle.

Over 2-3 million bats of 12 species inhabit the roof. They devour 30 tonnes of mosquitoes, nocturnally! If the roof looks dense black due to the clinging bats, then the floor and railings look dark due to guano (bat droppings), some of which may even drop into the mouth as one looks up in awe at the crescent ceiling. Guano is food for hosts of cockroaches and beetles jostling on the floor, as in the film The Mummy.

Outside the Deer Cave is the Bat Observatory, where one can view millions of bats exiting the cave in search of insects between 4pm and 6:30pm daily. They spiral out in hordes to avoid being prey to bat hawks waiting for them on the cliffs. Rains can spoil bat-watching plans, as it’s difficult for bats to echolocate flying insects during this time. But they unfailingly venture out on clear days. The walk back to the park office in the dark, at around 7pm, is stimulating in torchlight amid the sounds of gushing mountainous rivers, croaking frogs, chirping crickets and zipping fireflies.