February - 2019

Mulu Caves ’96 – Hidden Valley


- edited from an article by Tim Allen in Caves & Caving Magazine – Spring 1997

The Hidden Valley forms a striking feature on the slopes of Gunung Api. With vast limestone cliffs towering 500m above its floor the deep gorge cuts westwards into the side of the mountain providing drainage for the slopes of Gunung Mulu. All the modern day water entering the valley sinks into the limestone to follow underground routes through the mountain to the Melinau Paku River. The sinks are choked by sediment and debris, however dye tracing has shown the waters to emerge at Nasib Bagus (Sarawak Chamber Cave) and Cobra Cave.

The heli lands close to the cliffs in the Hidden Valley | photo © Tim Allen

Beyond the sinks the valley continues westwards, rising up onto pinnacle karst before leaving the cliffs and turning south towards the Paku valley. Here, the valley runs through a landscape of cone and pinnacle karst with its route dominated by deep dolines. These dolines hold great potential for cave exploration. The ground is extremely harsh, totally different to the flat alluvial plain in the gorge or the sandstone slopes of Gunung Mulu. Due to its severity, even the nomadic Penan have never ventured beyond the alluvial plain to hunt or gather fruits, leaving a large area of karst landscape totally unexplored by man.

The Hidden Valley was first visited by cavers in 1978 as part of a Royal Geographical Society Expedition. Such a striking karst feature could hardly be ignored and during a brief camp in the valley, Prediction Cave and Wonder Cave were discovered. Little progress was made out of the flood plain onto the dolines. One member of the team fell seri­ously ill and had to be heli-evacuated out of the valley. The expe­dition report concluded that Hidden Valley was home to ‘the most inhospitable terrain known to man’.

Since that time no expedition has re­turned to the Hidden Valley. All the atten­tion has focused on the western side on such fine caves as the Clearwater/Blackrock sys­tem now standing at 107km in length. The last Mulu expedition in 1991 began to run out of significant leads and the idea of a return to Hidden Valley was first muted.

In January 1993 Matt Kirby, Dave Gill and myself amongst others were back at Mulu National Park Headquarters preparing for a six day recce to the Valley. Little information was available on the logistics of reaching Hidden Valley as it was 15 years since anyone had been there. Estimates of walking times varied from two hours to two days! In the event we spread the walk in over two days but realised it could be done, at a push in nine hours. Three full days were spent in the Valley itself but not a great deal was discovered.
There were a number of entrances high in the cliffs but access to these would involve serious climbing. Lawai, a National Park Guide, located a promising entrance in the second doline but by then it was too late to explore its potential. We had however de­termined the potential of the rain, mud, flooding, leeches and ‘the most in hospita­ble terrain known to man’! It was somewhat of a surprise then three years later to receive a phone call from Matt, “About time we went back to Mulu… Hidden Valley… Dave might be able to get a heli… are you interested?” Three years seemed to have dulled the memory enough. The timing was perfect. “Book me in”. I said.

Expedition veteran, Dave Gill, was work­ing for the Sarawak Forestry Dept. Dave wanted to involve the Forestry Department in more original exploration within Mulu National Park and so the expedition became a joint venture. The advantage to us was that the forestry would provide guides and por­ters and most importantly a helicopter.
A team of eight Brits was assembled, Mulu veterans Matt Kirby, Richard Cham­bers, Pete Boyes, Pete Smart and myself together with Mulu virgins Mick Nunwick, Mark Wright and Nick Jones. Royal Brunei Airlines would fly us out to Miri, the state capital of Northern Sarawak, where outfit­ters Tropical Adventure would take care of all land arrangements.
There were bound to be a few surprises in store on such an expedition. However we didn’t expect the first so soon. In the departure lounge of Heathrow Airport a young Danish girl introduced herself as a member of the expedition. This was news to us, but it transpired that she and her younger sister had been invited as guests of the Forestry Dept. They would be joining us in the Hidden Valley for ten days.

The cramped Hidden Valley camp | photo © Matt Kirby

Eventually all the supplies were organ­ised in Miri and we flew up to the Park. A team of three Mulu National Park Guides and three Penan labourers had already left for the Hidden Valley. Laden with a chainsaw and fuel their job was to cut a helipad and construct camp. Although we could all have flown in by heli we made it a rule that all the Europeans should walk in. This was mainly to show everyone just how remote and hostile Hidden Valley was. What with the airport, hotels, plank walks and show caves Mulu nowadays has the air of a theme park. Step off the plank walk away from headquarters, however, and you’re in a dif­ferent world entirely.
As the ‘78 expedition found out illness or accidents can be potentially very serious. Med-evac by helicopter can not be guaran­teed with bad weather causing problems. During the recce we had established radio contact between the Valley and Park Head­quarters via a booster station on Gunung Mulu, but lightning had put this out of ac­tion. We were going to take a single side band set with us though there was little hope of it working from the depths of the Valley.

Five of us set off for Hidden Valley at first light together with Charlie our cook and Tama Jarau our Penan guide. Tama Jarau had been our guide in ‘93 and was a great character from the old hunter gatherer school. Even at 50 years old rumour had it that he could run round Gunung Api in less than a day. The first couple of hours of the walk are along the flat of the Melinau Paku Valley following a wide trail which eventually leads to the summit of Mulu. We cut off this onto a ‘track’ which only Tama Jarau could see. After winding our way up and down, and crossing several rivers we arrived at the foot of a 1000m climb up to the top of the ridge separating the Paku from the Hidden Valley. We all got fairly strung out on the way to the top and poor Charlie got left behind. It was pouring with tropical rain and the leeches were having a field day. I found twelve down my sock during one stop. While we waited at the top of the ridge we tested the radio set. Contact was made with a logging camp who could relay messages to Park Headquarters in case of emergency.

Charlie, however, still hadn’t shown up and it was now mid afternoon, with a couple of hours still to go to camp. We decided to split up, Matt and l would go back for Charlie while Richard, Mark and Mick would trail blaze to camp. We signalled to Tama Jarau to cut us a ‘motorway’ which we could follow in the dark if necessary. Charlie was found over half way back down the hill. He was sat under a camp sheet sheltering from the rain, exhausted and probably regretting he’d ever taken on the job as cook. We split his load and got him to the top. It was now only an hour before dark. I took the biggest load while Matt agreed to nursemaid Charlie. This turned out to be a good move for me as I soon found myself way ahead. Tama Jarau had been true to his word and the track was relatively easy to follow. The first section into the valley is incredibly steep dropping 500m to the river after which the going becomes easier. I was grateful to make it into camp only an hour after dark. Matt and Charlie were not so lucky and limped in some three hours later.

The advance party of Park Guides had been busy. The heli pad was cut and the framework of camp erected. Lawai was in charge as he had been to the Valley in ‘93, Chris and Syria were less experienced.

The following day the heli brought in three loads of food and kit together with Dave Gill and Pete Smart who had defied the walk in order. Tama Jarau took a ride out on the heli. He was to walk in again the next day with National Park Wildlife Officer, Rambli Ahmad, Nick and the Danes. The heli had ten minutes of spare fly time and as we were nearest Richard, Mark and myself commandeered a quick flight over the val­ley and dolines. Spectacular as it was no entrances could be seen through the thick tree canopy. From the air the heli pad looked tiny and the pilot had had trouble finding it on his first run. However, back on the ground it was the biggest thing in our world and would remain so for the next twenty-two days.

Tim Allen climbing to an entrance above Prediction Cave | photo © Matt Kirby

One of the first objectives of the expedi­tion was to investigate some of the entrances in the cliff faces. We had brought a range of climbing equipment specifically for this purpose. We were unsure as to how many entrances there were because they were so hard to spot through the dense jungle canopy. It was a case of stumbling about with eyes aloft looking for that one small gap to see through. One particular entrance was spot­ted 150m above the valley floor. This was eventually reached by climbing steep scree slopes and vertical rock. Friends, nuts and quick draws we had a plenty but the most essential piece of equipment for this type of work was a parang. However, what had looked a sure bet from down below was only a huge alcove. From our vantage point we did get a good look at the opposite side of the valley and noticed another promising entrance 70m up. The climbing was harder here and in­volved chimneying up between a tree and the cliff face. As Mick made the move back onto the face a hold came away and he fell. He ended up swinging in space at about the same level as my belay stance. Being a man of few words he only said, “lot of slack”, before jumping back on the route! We topped out after four pitches only to find another slightly deeper alcove. Dave, Pete and Lawai pushed up into the karst to the second doline and refound the entrance discovered by Lawai in ‘93. Over a couple of days the whole team explored nearly a kilometre here. A 20m entrance pitch led into a can­yon passage with a small invading streamway.  A further climb led downstream but the water sank in fissures in the floor and be­yond the passage soon became choked with sediment. A pitch through a narrow gap in boulders led to the floor of the upstream section. The gap at the pitch head was the home to a cave racer snake who lurked at the narrowest part catching his diet of swifts on the wing. Fortunately he soon slithered away when we approached.

Upstream the passage choked again with sediment and a side lead led through a big chamber to an aven. At a later date this was connected to a shaft next to the surface track by the Park Guides. The cave was named Arch Cave due to the shape of the entrance passage.
Another initial objective was to re ex­plore Prediction and Wonder Caves.  Predic­tion cave must have been a monster of a passage that became rammed full of sediment.  As the sediment dried and shrunk it has left most of the passage only a few metres high but the width extends to 100m in places. Gaps down the side of the sediment suggest a depth of over 40m. The ‘78 surveys showed a number of question marks but these amounted to very little. Mark noticed some holes in the cliff above the main entrance which were too promising to ignore and another climbing operation swung into ac­tion.
The whole face was severely overhang­ing but we did have a drill with us. An ingenious start was made by prussiking up a tree trunk then tensioning the whole tree over to the cliff face to get the first couple of bolts in. From here it took two days of the most strenuous bolting either of us had done to finally get into the passage. The buzz of the climb only just compensated us for the discovery of yet another alcove.
Wonder Cave was nearly 4km long and consisted of a number of small passages which connected some major trunk routes segments. The ‘78 survey showed the siren draught coming down an aven at the end, an obvious possibility. Mark, Richard, Chris and Syria located the cave via a new en­trance and soon found themselves in a small, steeply descending passage consisting of pitches, climbs, traverses, grovels even a squeeze so tight you had to take your gear off. The worst section was a low, wet, muddy crawl with razor sharp veins of calcite under the mud. Beyond this a ramp ascended to join a trunk segment. It was here that an in-situ rope broke on Mark as he climbed up a sediment bank and the group turned for home. Beyond the sediment climb, the route drops into another grovel before rising up into the Elephants Graveyard, a huge boulder strewn chamber. From the far corner an undulating tube continues to the end.
Mick and Nick were next to take up the challenge. They descended to the muddy crawl only to find it sumped! Heavy rains the day before were responsible and as it rained most days this could become a bit of a problem. Next day finding the sump had lowered to a duck they continued towards the end. A hundred metres from the final aven disaster struck. As Nick crossed a short traverse on another in-situ rope it broke, and he fell 12m onto a bouldery floor. His injuries were quite serious, most obvious being a deep four inch laceration across his forehead just below the helmet line. With pains also in his lower back, abdomen and upper thighs he was in a bit of a mess. It appeared he had landed bum first on a pinnacle of rock and then been propelled forward onto his head. After assessing their situation and resting up a while they began the slow painful journey out. Nick, being the strong lad that he is made it out in five hours, greatly assisted by Mick. The entrance series was particularly un­pleasant but at least the airspace in the duck had lowered.

Dr Pete Smart stitches up Nick's headwound | photo © Matt Kirby

Back in camp Pete and Richard cleaned Nick up and put about ten stitches in his head. He was put to bed with a couple of painkillers and an unusual quiet descended over camp. The whole team were concerned,  Nick would have to go to hospital as soon as possible and that meant bringing a heli in. The evacuation began at dawn. Tama Jarau legged it round to Park Headquarters with a message, whilst a team climbed up to the ridge with the radio and tried to establish contact. Those of us left in camp first knew of the success of the plan when the heli arrived. Tama Jarau had beaten the radio team to it with his message, arriving in the Park in an incredible four and a half hours. Mr Ting of Tropical Adventure had had to pay £1000 cash on our behalf for the heli. Nick was flown directly to Miri hospital, accompanied by Mick who was to travel with him all the way home if necessary.
Morale was at an all time low. With Nick and Mick gone we felt under­manned. Several of the remaining team had Mulu foot and other minor tropical ailments. We weren’t even finding much cave. On top of this the living conditions were harsh. Camp was often a miserable place, damp and dingy under our leaking camp sheets. With the heavy rain came flooding and twice Charlie’s kitchen was washed away. As for the toilet, it wasn’t so much squalid as alive. Squatting over a hole that croaked surrounded by a swarm of bees, it was soon dubbed it ‘the most inhospitable toilet known to man!’

Syria at the head of the main pitch in Damocles Cave | photo © Matt Kirby

There was nothing to be done but to get on with the job in hand. Pete S and Matt cut their way into the third doline and found Perseverance Cave at the foot of the cliff. Three entrances had all been filled with sediment but one had been washed out by an invading stream. This led to a network of passages just short of a kilometre long.  Dave and the guides located Damocles Cave in the obvious place, at the end of the valley. It had been missed by everyone else. The entrance passage led to a spectacular 40m pitch down to an active streamway. The way on continued open but was not pushed very far due to the risk of flooding. A wise precau­tion as ropes left in for a later photographic trip were trashed. Another large choked entrance nearby hinted that there was a lot of development in the area and that perhaps we were only just missing the big one.
Three days after Nick’s accident, much to everyone’s relief, Mick crashed out of the jungle and into camp. He was accompanied by Pete Boyes who had flown out from the UK a week after us. Nick had only spent a few hours in hospital where they had stitched up some more injuries to his abdomen but had declared him fit to travel. They even praised Pete’s stitching to his forehead. Tropi­cal Adventure had him on a plane home the following day where by all accounts he endured a most uncomfortable 18 hour flight home.
With Pete B and the return of Mick, the team was back to strength. The Danish girls were also due to leave the following day. They had done lot of surface surveying, helping to tie together all the entrances, invaluable work in making sense out of what we had found During the med-evac flight out, Mick had spotted a large entrance above the western side of the third doline. Mick, Mark and I planned to try and find it the following day.
Our plan was to cut off the track some­where between the second and third dolines and contour round. We knew from our heli reconnaissance that a fourth doline lay be­yond the third, separated by a high, narrow ridge. We hoped that by crossing this ridge it would take us to the area where the Helicopter Cave lay. Cutting track in this terrain has to be experienced to be believed.  Imagine an extremely eroded pinnacled land­scape, cover it with the leanest of top soils, add undergrowth so dense you can’t see where you’re going and presto, Lowes Gully – a picnic!. Progress was slow, the ground often impassable and direction constantly altered.
We passed a stal choked entrance before reaching a deep gully. A natural rock bridge spanned the gully and below it on the far side was a large entrance – it looked a goer! We climbed up to and across the bridge which was 10m long but only a few meters wide and deep. Mark checked the cave out for a couple of hundred metres while Mick found a deep shaft in the side of the gully. Prudently we decided to carry on with our ‘walk’ while our luck was in. Bridge Cave seemed a simple enough name for our new find.
We continued onto the start of the ridge. The whole area was just a mass of 10m high pinnacles. We climbed up, down, around, in, out and over but the ridge fought us off and we were forced down into the fourth doline. This wasn’t so bad at all as we were sure we could make out the vague outline of a really large entrance through the trees. We raced down, parangs flying, to a cliff above the entrance. It took another hour to find a way down.
Once there, however, we knew we had cracked it- it was massive. We descended a boulder slope for a few hundred metres and came to a pitch of about 40m. It was as if we were in a roof tunnel and the pitch led to the main passage. The roof however, remained flat and since the roof was as far away as the floor we were looking at a passage some 80m high and probably 40m wide.
A few hollers had the echo bouncing into the distance we just knew it was a biggee. The entrance had its own little cloud so we called it Cloud Cave. We set off back to camp welI pleased with the day’s work. We reckoned we had travelled only 700m from the main track. This gave us 100m of progress for each hour of trail bashing!
Back at camp the day’s success was wel­come news indeed. We divided up the spoils only Pete B and Mark were disappointed. They got the shaft which turned out to be 60m deep to a choke. Mick, Lawai, Chris and myself returned to Cloud Cave for a two night bivi. We dropped the pitch and found that the passage continued in both direc­tions.
Heading back towards Hidden Valley we followed a large passage up to 45m wide. It was obviously old with lots of breakdown and dusty guano. Along the length of the passage inlets entered from the roof creating islands of stalagmites.
A short choke was easily passed to more of the same until a forest of stal on a false floor ended exploration at an overhanging pitch. Crab Inlet was discovered nearby, partly hidden behind a mound of sediment. Exploration was stopped here at a wall of large boulders with the passage continuing overhead. We headed back to the bivi pleased to have a kilometre in the notebook. In daylight, the bivi site had seemed pleasant enough, out with nightfall matters had taken a turn for the worse. Hundreds of thousands of swifts flew round above our heads as we cooked tea, the noise was deafening and we were bombarded with guano, feathers and dead and dying birds. Just as we thought it couldn’t get worse a swift crash landed in the soup.
Tea was best eaten with the lights out. As bivouacs go this was definitely fourth divi­sion stuff. Not to be beaten Chris and Lawai disappeared into the jungle and returned with armfuls of palm fronds. Within half an hour these were woven into a bird proof shelter and camp misery was transformed into the five star Palm Beach Hotel!
Next day we returned to the pitch at the end of Cloud Cave. Only a short distance was gained before a huge slope rose up to a very terminal choke. Back at the en­trance pitch a steep slope headed in the opposite direction.
We surveyed 200m in a straight line at a constant angle of minus thirty five degrees down to the bottom and the roar of what sounded like a large river. Sure enough a little further on and a foaming torrent poured out from boulders and down a pitch. We had no tackle left but knew this was the river that fed either Cobra Cave or Nasib Bagus.

Split passage in Bridge Cave | photo © Matt Kirby

We spent the rest of the day checking out passages around the entrance. A number of heavily potholed passages in close proxim­ity to each other all ended in pitches. The most promising lead, however, was nearly written off as an alcove.
Obscured by a jumble of breakdown a big passage headed in the direction of the Paku Valley. It ended at a 30m pitch into something even bigger with never-ending echoes. We were surface surveying back when Mick received the ultimate personal insult, a leech up his trousers!
In Hidden Valley camp the rest of the team had been enjoying even greater suc­cess. Bridge Cave was already over 3km long. Operating from a bivi a few hundred metres inside the entrance the team were into classic Mulu passages with white lime­stone walls and dry guano covered floors. A network of interconnecting passages on a number of different levels, orientated between the Hidden and Paku valleys, be­gan to appear on the growing survey. Almost every junction seemed to open up new frontiers. Once the initial surveys had been drawn up it confirmed that Bridge Cave crossed over some 100m above Cloud Cave.

Several more trips were made to Bridge Cave which kept going and going. At the Hidden Valley end a huge shaft named the Abyss was found. Located above the end of Cloud Cave a connection seemed possible. At the Paku end several passages were still going. One had broken out onto the surface but another continued deep into the hillside. Bridge Cave eventually grew to over 6km long with many leads remaining and was the most significant discovery of the expedition. Unfortunately the closest I came to the cave was the entrance, hence the lack of narra­tive.

Mick Nunwick dispatches a boil, then continues caving | photo © Tim Allen

Many of the team were now suffering from minor recurring tropical ailments. Mulu foot and large festering boils were rife. This affected our ability to push the caves in the closing days. Dave, Mark and Syria set off to push Cloud Cave however they returned the next day having achieved nothing. Mark’s knee had swollen up to balloon proportions, Dave was vomiting and Syria got a huge boil on her bum.
Two more trips were made into Wonder Cave and a climb at the terminal aven led to 200m of big stuff before ending in a choke. No one was particularly sorry to see the back of that one. A two day attempt to locate Helicopter Cave failed due to the rough terrain. How­ever, it was actually sighted from one par­ticular place and it did look good. Also a route into the western valley leading to­wards Clearwater was found.
This area has great potential but the logis­tics involved excluded it from our attentions on this expedition. Pete Smart was the only person to visit all the caves in a manic quest to look at mud. Pete B was the only one who came close to keeping up with him. The results of his scientific work are still been collated and will be reported at a later date.
It would be true to say that life in the Hidden Valley was grinding us down. Cer­tain people had even been seen boarding an imaginary helicopter on the pad.

A flood washes through the camp kitchen | photo © Matt Kirby

So it was with no great sadness that the last caving day arrived. We did, however, have grandiose plans. Matt was to photo­graph Bridge Cave (the results of which were that good he wished he had taken more), Mark wanted to drop the 30m diameter Abyss but despite taking 90m of rope couldn’t reach the bottom. Mick and I would return to Cloud Cave and check out the river passage.
We rigged two short pitches down to the river. The passage walls had closed in and after only a few tens of metres were down to just half a metre wide.
Mick pushed on through a duck to the head of a cascading 15m pitch. This was not the place to be in a flood so we surveyed out. Back at the pitch head whilst waiting for Mick to answer a call of nature I began to study the roof. Behind me it soared into the distance but in front it was only a few metres high. Something up there, I thought. With a bit of a traverse and a grovel under some boulders I popped up into a parallel passage. Searching around I found some footprints in the mud. I followed them around but they just kept leading to dead ends. Mick arrived and with difficulty we traced them to a traverse over deep holes. This fitted the description of Cobra Cave perfectly.
The connection had been made bringing the combined total to 5.6km. With time still on our hands we returned to the big passage near the entrance and dropped the 30m pitch. We landed in what must have been the continuation of the main route. Big as it was the going wasn’t easy as huge decaying blocks crumbled beneath our feet. After half a kilometre we were halted by a short pitch with the way on stretching away in front. We called it the Last Tango in Mulu and stum­bled back to camp in the dark.
Next day everyone and everything was helicoptered out as planned. No one had yet mentioned returning to Hidden Valley. How­ever the expedition had discovered and only just begun to explore a multi level system over a vertical range of 400m. It was only a matter of time before we would be planning the next expedition into ‘the most inhospitable terrain known to man’.