The World’s Largest Underground Chamber

Picking your way over the rocky slope the walls are at first comfortingly close. But as you labour away at the unending slope you are suddenly overcome by apprehension, an unnerving sense of immensity beyond your knowledge,  a frightening scale of darkness. Thank goodness for your friends, small dots of light to hold fast to in the inky blackness of the world’s largest undergound  cavity – Sarawak Chamber.

Sarawak Chamber. Photo © Jerry Wooldridge

Eight jumbo jets easily span the chamber whilst Britain's largest chamber fits into the entrance passage.

Sarawak Chamber is universally accepted as the largest underground chamber in the world.  Discovered during the British-Malaysian Mulu ’80 Expedition, it has maximum dimensions of 700 x 400m and an estimated roof height of 100m.  The perimeter of the chamber has been surveyed and the eastern ‘half’ alone took, “77 survey legs each of 30 metres” to survey around.  The expedition published a conservative volume of 12 million cubic metres, but without more concise data this can only be viewed as a rough guide.  The surface area of the chamber can be more accurately calculated and has been published at 162,700 square metres.

Sarawak Chamber is located on the northern side of the Melinau Paku Valley about three and a half hours walk from Park HQ.  The chamber itself is a part of Nasib Bagus (Good Luck Cave).  Nasib Bagus is a resurgence cave for water sinking in the Hidden Valley and 1.5 kilometres of active stream passage must be traversed before the great chamber is reached.  It is possible to visit the chamber as an experienced tourist caver but these trips are difficult to arrange and are prone to cancellation due to flooding in the entrance passage.

Dave Checkley was one of the original discoverers back in 1980.  He recalls a memorable day:

Andy Eavis estimated that it was a two-hour walk to the Good Luck resurgence cave. However, we weren’t too surprised when it became a four-hour epic and we were relieved to drop our heavy packs at the entrance. Time was by then pressing so we headed off into the cave and left -our local support team setting up camp under a huge tree with snaking buttress roots. 

Jerry Wooldridge photographing the largest chamber | photo © self portrait

An hour’s fabulous sporting caving took us to the cairn marking the furthest point of Andy’s previous exploration. We got out our mapping instruments—a good excuse for a brief rest. I was taking the notes, Tony White would make the compass, clinometer and survey tape readings whilst Andy took photographs and helped out when the tape snagged on an obstruction. We set off slowly mapping the passage as we went, and it soon reached staggering proportions. The left hand wall faded from sight even in the combined light of our three headlamps, so we followed the right hand wall. We climbed up the steep rocky slope with the towering wall still dimly in view. The number of survey stations slowly mounted. The roof disappeared from view. Was it a chamber or just a huge passage? The roar of the river grew fainter behind us. We chatted and speculated about this huge black void we found ourselves in. This was big even by Mulu standards. As time went on I was starting to have problems guessing the distance to the wall—was it 50 metres or twice as far? The wall was our only point of reference, and I insisted we got closer to it. What could I draw if I didn’t have the wall close at hand— just an immense rubble slope? We surveyed straight towards it—amazingly it was 100 metres away. Distances can be confusing in such huge cavities. The slope was often steep and we likened it to climbing a long scree slope up an English mountain, but climbing it in the pitch dark. Andy was starting to get excited about it being the biggest passage in the world. Tony was as cool, calm and collected as ever. My feet hurt.

We followed the wall into alcoves and out again, not really knowing what they were until we had mapped them. We hit a huge smooth face—clearly a fault line where rock had ground against rock and been polished in the process. After the fault we began to turn. Slowly but surely, the compass bearings told us we were curving round to the left. Perhaps it really was a chamber and not a passage— after all, we could still hear the river faintly in the far distance. We struggled on for twelve hours. By this time we had stopped joking and chatting and the echoing silence was only broken by Tony’s voice calling out the instrument readings. Even Andy had stopped speculating on which record we might break. It was four in the morning, we had reached our hundredth surveying station. We were exhausted and decided to call it a day. Even Tony didn’t take much persuading to stop, although he rarely likes to leave a survey incomplete. My feet were on fire and I could hardly walk – another case of “Mulu Foot” was on its way.

Surveying in Sarawak Chamber | photo © Andy Eavis

To try and determine whether or not we were in a chamber we decided to walk back on a compass bearing heading towards the noise of the river. We scrambled down amongst giant blocks and got half lost in a boulder filled valley. The noise of the water drew us on and we eventually reached the river and were a little relieved to find the cairn Andy had built. We clambered back down the cascades and reached the canal. I dangled my feet over the edge of the boat on the paddle back – the water seemed to cool and soothe the throbbing pain. We reached camp just before dawn to find Danny waiting up for us – what a good man. He cooked us a meal and we grabbed a few hours sleep before the sun rose fully, and it was time to head back to base camp.
When we got up my feet were agony. I walked back in sandals – I would have crawled if it had been nearer. It wasn’t until we drew up the survey the following day that we realized that we had found by far the biggest chamber in the world—we just had to call it Sarawak Chamber. It was a fitting end to a wonderful expedition.

For further information log on website :
http://www.mulucaves.org/wordpress/expeditions/hidden-valley-93