Tues 19th Nov - Guranng Mulu National Park - Sarawak

I first heard the name Mulu more than twenty years ago. I suspect I may have first seen it in a feature in my perennially favourite magazine The National Geographic, though it was definitely written at the top of the page that fell open first in my Underground Atlas acquired in a bargain bookstore in the mid-nineties. My teenage sport of choice - rock-climbing, was the gateway into the more gothic, underground equivalent of caving. Caving and speleology for me had the Romantic associations of fantastical Jules Verne style expeditions into the last uncharted frontiers of our planet. It was because I never seriously undertook any such caving that this rose-tinted view persisted. Only later did I experience at first hand the rather soggy, distinctly unglamorous, squeezes and muddy sumps of small dank potholes in northern English counties, shedding the sodden boiler-suit and flat head-torch for a parochial pint of bitter after.

Nevertheless the names Mulu and Sarawak endured talisman-like in my conscious as the semi-mythical location in darkest Borneo of the world's very biggest caves, hidden amongst impossibly dense jungle and populated by insects of prehistoric scale. It was with this at the forefront of my mind that I'd booked tickets from Vietnam, and found a direct flight up from Kuching. It was also why I was a little disappointed when I saw we were going to be flying on the large commercial aircraft shown below, rather than the tiny six-seater, flown by a deranged bush-pilot with a side-line in gun-running and black-market artefact exports that I'd been imagining.

To further the misapprehension of my own adventure, I'd accidentally booked myself into business class! I couldn't believe they even catered for such cosmopolitan concerns, but there it was. I got addressed by name at the back of the plane and was offered a shrink-wrapped apple, three sets of plastic cutlery, and a segregating curtain for the ten dollar supplement on the 45 minute flight.

Within half an hour of waking the ground crew from their afternoon slumber, we collected our bags from the tiny non-conveying belt and jumped in a Land Rover for the one mile journey from Mulu airport to Mulu Gunaang National Park HQ. I was booked into a dorm at Park HQ for the next two nights, my first dorm in a while. It was fairly quiet, so a chose a bed in the corner, near windows with the least number of tears in the mosquito screens.

I'd signed up for a few guided walks and adventure tours around the park, starting that afternoon with a journey to the centre of the world's largest cave passage*.  The three kilometre walk from park HQ to the Deer Cave was along a wooden boardwalk through thick rainforest, large areas of which were currently submerged by normally small streams now flooded by recent heavy rain.

I was immediately in love with this place. Words like bio-diversity are bandied about a lot at the moment, but here in the jungles of Sarawak, that word becomes real. Life in so many forms was everywhere. The trees, plants, flowers, creepers, lianas, vines, ferns, palms, and mosses were crawling with critters of uncertain origin. I counted at least five varieties of dragonfly, seven types of butterflies, and as many different types of ant while there, without even trying. The jungle is loud - insects, birds and frogs all competed to get their mating calls, and warning cries heard above the din. 

I was rapidly reminded that I was just another cog in this incredibly grand design. I am but a host for my genes, like myriad others, competing to deliver copies of themselves into the next generations. I was also becoming aware (paranoid even) that everything here, including myself, was trying to subsist, or even thrive, whilst avoiding becoming a meal, or a home, or both, to another hungry competitive life form. Size doesn't matter - very, very small things eat very big things here. My position as top predator in the neighbourhood was somewhat in jeopardy, given my lack of jungle guile and city dwelling ways. 

Look closely at the picture below, underneath all the foliage you should be able to make out thin blades of sharp rock rising three to five feet from the jungle floor. These are made from limestone karst and are the harder remnants of the previously higher floor, now carved away by the corrosive action of CO2 in rainwater. Navigating this terrain would be tortuously slow and injurious for a human, so am very grateful for the Herculean efforts of those who built the 3km walkway over this living minefield. But this karst is why I was at Mulu in the first place.

After 3km on the boardwalk, through the forest canopy we saw a cliff rising from the jungle above us, to maybe 1000ft. Approaching it closer through a security gate we began to get a sense of the massive overhang that formed the mouth of Deer Cave. The peaty, acrid smell of bat guano became noticeable and we could see hundreds of streams of water pouring from high above us to the jungle floor. Far too small to be considered waterfalls, they nevertheless together created the sense of a veil, not occluding, but at least signifying the entrance to cave.

We were on a low path on the far left hand side of the entrance, the floor of this cave had rotated upwards in the millions of years since its formation and it was now tilted at a steep angle. High above me on a cliff within the cave mouth were tall palm trees dwarfed by the scale of this vast cavity. I could barely make out the tiny, swooping dots in the mid-ground that were Swiftlets, the daytime foragers of this environment.

Jaws open, like the cave itself, we walked inside, necks craning, struggling to find indicators of scale on the distant walls and ceilings. Far ahead of me people on steps ascended a small traverse, while far beyond them the cave continued deep into the mountain, losing none of it's colossal cross-section along the way.

We passed a huge river raging through the lowest part of the passage, carving it yet deeper for future generations to gawp at. After half an hour walking we arrived on the top of a hill of fallen rock some 100ft above the floor and gazed out in awe across the chamber at the other, more hidden far entrance to the cave. Known as the Garden of Eden, it looked every bit the part, with lush verdant jungle spilling down the scree slope into the enormous cave mouth. 

We returned the way we entered, looping back around huge speleothems, taking note of formations that looked like president Lincoln's profile silhouetted against the sky; and stopping frequently to struggle to capture the space on camera. Multiple HDR exposures may get the light range, (and I'll post them when I eventually manage to process them) but these still photographs cannot hope to give an idea of the depth and scale. There is in these images virtually no sense of the dimensions of this cave, but imagine a space 500ft wide, 400ft tall and over a mile long and you might get the picture. It's truly breath-taking.

Exiting the cave just before dusk gave us the chance to see the other big tourist draw here - the bats flying out. Deer Cave hosts a uniquely diverse population of bats. No fewer than seven species claim this cave as their own, numbering some 3 million individuals. On a clear day, for the hour around dusk they all leave the cave in spiralling ribbons, streaming through the sky over our heads. It's reckoned they consume about 30 tonnes of insects, mostly mosquitos, per night, which makes me love them even more, considering the state of the screens in the dorm that I was staying in that night.

*Despite the fact that Vietnam's Son Doong (explored in 2009 by Howard & Deb Limbert, and narrowly missed by me in October 2013) has now been shown to be considerably larger, Mulu haven't yet bothered to change their literature or posters - The world's second biggest cave isn't such a draw. 

Read a brilliantly written account of the first successful push of Son Doong here:

http://ngm.nationalgeographic.com/print/2011/01/largest-cave/jenkins-tex