Jomblang and Grubug Vertical Caving, Underground Art of Excitements

(versi edit telah diterbitkan di Jakarta Post 29 Agustus 2010)

Oleh : R. Heru Hendarto

Crescent moon has slipped over the night when we entered the village. Dark’s night scenery made us disoriented since the surroundings looked similar. As we lost and missed the entrance sign board, one motorcycle guided us in, and slowly driving bumpy on stony village road for 15 minutes. At last finally, we lay over our exhausted body on the pendopo floor, trying to get some sleep to face the next day.

The beautiful sunrise accompanied us, raised among the shade of teakwood trees surrounding Jomblang area.  Situated around 17 Km from Wonosari city (40 km from Yogyakarta capital province), this cave is not quite famous for common people. But, among cavers, nature trekkers and backpackers, Jomblang cave is already well known since the last two years for its beauty. As a natural cave built on limestones, Jomblang provided a quite long line for vertical caving which is gave excitement to most people. Besides the vertical line, Jomblang also connected to Grubug cave in horizontal path. The fact is, most of the Gunung Kidul karsts high terrain comprised limestones, and by its nature soluble to water, creating hundreds of beautiful caves inside. Also due to its porosity, instead of its dry landscape on surface, there are huge natural water deposits beneath flowing as underground rivers.

After warming ups, our guide showed us the tools and the right way to use them. As a rookie, I didn’t recognize all of those tools except for karabiner, helmet and harness. After 10 minutes, I realized that climbing tools divided into two major parts, descending and ascending. Descending involving tools such as hip harness, jammer, and the most important thing is descender stop. For ascending, there are some extra tools added such as chest harness, foot loop and ascender. I didn’t force my brain to memorize them all in a short period of time, instead of trying to understand the mechanical way and how to use them correctly.  And of course, we also got our trial session by applying the descending and ascending on the tree before ‘entering the real battle field’.

Then here we were, standing in the rim of Jomblang mouth at 10.15 in the morning. There were two vertical lines available, the one on the north side and another line approximately 100 m across the mouth. The first line has 63 m depth and the last line only last for 15 m, so that they called it VIP line. As a beginner, we actually had to take the VIP line but at the time the guide challenged the six of us to go down through 63 m line, we accepted it. First participant went down, and it took almost 20 minutes for her to reach the bottom. Considering the preparation needed and travelling time to the bottom, I and a friend decided to take the VIP line to save some time. Actually, I had a purpose also to take pictures from below, so we moved across.

They called it VIP lines of course with the reason that this is in fact the easiest way to reach the bottom. First we had to get through the inclined wall from 30 to 80 degrees by rappelling. After approximately 20 meters high, then we had to go through 15 m vertical cliff using Single Rope Technic. It was not quite hard though, except for a ‘stiff thumb’ feel on my left hand. The rope we used already expand larger in diameter due to long usage, therefore it inhibits descender stop to work well. Most of the time I got to press harder with my thumb just to make the rope loosen and moved my body downwards. Since the rope diameter was not fit enough to the descender, I got jerky down travel. Bumpy, and sometimes got stuck for a moment in the air with adrenaline rushed in the blood. Although the rope load capacity was 120 kg, I still had to learn to be calm to ‘count my life’ just on a piece of a rope. It was not easy for me, the one whom never really trust in the mechanical tools anyway. The similar problem also faced by others, their descender stop became hot and forced them to cooling down the tools by resting in the air for couple minutes. “I hope I put the vidcam on my helmet to tape the remarkable view from 40 meters up there”, said one of the participants.

At 12.30 we all managed to reach the bottom of Jomblang. It was quite surprising though to witness that the cave bottom just looked like a tropical forest. High hard trees and bushes are grown everywhere above the brownish soil. No wonder, because that area are widely open and sunshine can get through them. We walked towards a large chamber on the north side. The size of this chamber is enormous, approximately 80 m high and 50 m wide. We were just walking on slippery and humid soil inside, following the path artificial stones that already settled there. I thought that the horizontal path connecting Jomblang and Grubug was long enough, but only 150 m later I was approaching the entrance mouth of Grubug. There goes my camera’s tripod, two flashes, one wireless trigger and two receivers since I could not get any remarkable objects to document around the path.

But then “Wooow..!”. I could not keep my mouth shut when we witnesses one of the most beautiful underground scenery of our lives. At the time we entered Grubug, we saw tens of beautiful ray of lights entering from the top of cave. I was told before that between 11 and 13 noon, the sun lights will go down to the bottom of the Grubug, creating a magnificient view underground. But for me this one was really different, We didn’t get merely a sun light but a lot of roll of lights instead! It was 12.40 when sun was high and its ray radiating through the leaves of the trees above, dividing it into shiny rays of light.  I grabbed a camera and then took a lot of photos, realizing that that view only last for 15 minutes! Tens of lights then merged into one big diffuse light.

Grubug cave consists of bedded limestone of calcarenite type. It is not common for underground cave to develop in those kinds of limestone since the hardness, solubility and other physical properties of the rocks differed from one bedding to another. That’s why I didn’t notice a lot of stalactites and stalagmites available, perhaps due to the material heterogeneity and lack of underwater drops. Usually, underground cave will develop inside limestones that come from reef origin since they have similarities in physical properties. In the middle of Grubug, I noticed two large boulders (speleothem) standing still. Those boulders developed from the soluble limestone by rain water, and creating white-bone colored calcite minerals. Those minerals were transported and going under lithification process, creating a wavy structure in the surface and pillar structure in the side. Right above the stones, there were 80 m descending line available. One whom likes challenge should try this Grubug descending line, which is only 300 m away from Jomblang. Below to the bottom north, there was underground river is flowing. In dry season where the water debit is low, people can track this river by rafting starting from River Suci and end up in this part.  The next part is impossible to track since the cave is so small although the water runs until it reaches the southern sea of Java.

We were started to go back at 13.30, heading to VIP line for another heaviest challenge, ascending. The first four managed to go up successfully. And on my turn, after succeeded ascending for 6 meters, I got cram on the shoulder.  It was not as easy as I thought although I already trained myself to have a pull-up exercise. Besides the pull-up, two important exercises are also needed, sit-up and squad-jump. The push force from legs, the stomach tension and the pull force of hand are the three combinations that have to manage to obtain optimum ascending movement. We have to put all of three into a smooth rhythm and well-body balancing, otherwise we will stuck by wasting our power for nothing. Also we have to realize the fact that, body weight inversely proportional to climbing ability. Well, have you seen a climber athlete with a fat body? So finally me, whom has a category of slight to medium overweight had to be rescued. Although ended up with quite embarrassment, I am fully enjoying the excitement of Jomblang and Grubug caving. Nice wonderful thing that you should try at least once in a lifetime!

How to Get there :

Jomblang cave is situated in Jetis village, Semanu, Wonosari District, Daerah Istimewa Yogyakarta. The only way to reach this place is using land transportation from Yogyakarta city. Travelling to southeast for 57 km, we will reached Jomblang in 1.5 hour.

We could rent a taxi or a car to go to this place. Using a motorcycle will be a lovely option since the scenery up there also quite nice.

Where to Stay :

We could stay in Yogyakarta city or Wonosari city and leave early in the morning or spend the night on Jomblang rest area. There are several nice cottages in the place, equipped with sufficient facilities such as electricity and water. The mouth of Jomblang is only 150 meter away.

Another cheaper option is to stay at the Jetis Wetan village Chief home, Pak Brewok.

What to Do :

Vertical caving, horizontal caving and underground photography are the most suitable activities in this area. Rafting, which is started outside cave from Kali Suci also become another interesting alternative. For all of those adrenaline-triggering activities, you should need a skillful operator and safety equipments. For caving, you can contact Acintyacunyata Speleogical Club (ASC) which has base on Kusumanegara street, Yogyakarta city. They are the first speleogical club that explored Jomblang and Grubug back in 1984. They are very professional, and can give you caving experience that you want.

If you added rafting activities, you can contact local tour operator such as Equator ( to provide you a good rafting equipments.


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