When in Borneo, Don't Be Afraid to Head Underground

Traversing “show caves” doesn’t require actual caving skills, but the payoff is still immense.

Getting out of the longboat in the heart of the Malaysian Borneo rainforest, I stared at the almost vertical wooden staircase in front of me. “It’s only 200 steps,” said my guide Albert, whose voice seemed to come from far away, even though he was standing right behind me. I was thinking of my right knee, the one I had injured a few weeks ago, the one that I had been told to protect from steep climbs.

Some of the mountains at Gunung Mulu National Park, like Gunung Mulu and Gunung Api, attract hardcore climbers. But visiting the caves at what locals call Mulu was not supposed to be strenuous. I’d read about the forest trails and boardwalk hikes, and had come expecting to breeze through on mostly flat terrain. But then again, I'd also expected caves to be subterranean. Why was I being urged to climb steps that seemed to be carved into the hillside? Albert assured me it would be fine, and as it turned out, the walk up was not that bad. There were even benches all along the way for me to stop, admire the scenery, and catch my breath.

More importantly, it ended up being so worth it, because Clearwater Cave was definitely the highlight of what are known as the local “show caves.” Geologists say that the mountains (gunung in the local language) there were formed due to tectonic activity between 2 to 5 million years ago, after which water from underground streams and rain—lots of rain, we're talking about the rainforest—managed to create a remarkable network of limestone caverns. It was funny to think that these intimidating limestone and sandstone rocks were also a result of rain’s gentle persistence.

And I am happy to report that, save for climbing up and down steps everywhere—and I mean everywhere—visiting these show caves did not require actual caving or rappelling skills at any point. You don’t even have to wade through rivers. I managed it quite easily over two days, even with my injured knee. 

longboats pulled up to shore in malaysian boreno near mulu national park
Photo by Charukesi Ramadurai

Exploring Clearwater Cave and Cave of the Winds

So, about Clearwater Cave. A half-hour longboat ride on the Melinau River from the boat jetty near the park’s main entrance gets you to what’s known as the Cave of the Winds. Named after the cool draught flowing through its dark and narrow passages, this cave has some of the most impressive stalactite and stalagmites in the area, as well as rock columns that rise up like finely chiseled marble pillars in the dim light. At the King’s Chamber—which is not, as I had assumed, named for its size—look out for the group of rocks said to resemble a king with his soldiers. (You’ll admittedly have to squint.)

Further ahead along the river is Clearwater Cave, which required all that aforementioned huffing and puffing up 200 steps just to get to the entrance. But this cave—one of the largest and longest in the world, at nearly 137 miles—is totally worth the climb, with the subterranean river that created this spectacular cavern still flowing in its depths along slippery smooth rocks.

Walking along the boardwalk to the constant background sound of gushing water, you will eventually come upon one of its most interesting features—the mini pinnacles. According to this documentary (start watching around the 50-minute mark) about the initial exploration of this cave system in 1980, microorganisms secrete fluids that corrode the rock and create a repetitive pattern with jagged edges that seem to reach out towards the sunlight. There’s also the Lady Cave, which features a stumpy stalagmite that seems to cast an eerie shadow of a woman on the opposite wall.

stalactites in a cave in mulu national park
Photo by Charukesi Ramadurai

Ducking into Deer Cave and Lang Cave

It’s said that Deer Cave can hold London’s St Paul’s Cathedral five times over. So, if anyone’s getting claustrophobic while reading this, it’s good to remember just how (literally) cavernous these caves are. Getting to the entrance takes less than an hour of hiking through the forest, but don’t rush. A few minutes from the mouth of the cave, stop and turn to look back at a silhouette that (really) resembles Abraham Lincoln’s profile. Your guide will know exactly where you can see this phenomenon. After you’ve clocked it, there’s then a good half-mile of boardwalk within the cave, finally leading up to the sight of what is called the Garden of Eden.

A large opening in the cave roof lets in sunlight, throwing the focus on the lush vegetation that thrives in this rainforest ecosystem. The green zone itself is reached by some more hiking and wading through water, and it has dozens of indigenous plants and trees that tribal communities use for natural dyes, medicine, and even food. Your guide will likely only know the local name of this flora, but look out for the jirak tree, which is covered in a bark that produces a red dye when boiled, or the bebata, a tree with edible fruit.

After exiting the cave, wait at the observatory outside for the bat exodus. More than 3 million wrinkled-lipped free-tailed bats—one of a dozen bat species here—roost inside Deer Cave and fly out in a swirling black mass every night just before sunset. Make sure to be there for one of the most impressive wildlife experiences in the area. And obviously, brace yourself for the ammonia smell and the occasional slimy brush with bat guano while inside the cave.

While Deer Cave awes with its size, Lang Cave next door has some of the most exquisite rock formations within this forest despite being the smallest of the show caves. Think stalagmites that resemble thorny cacti and stalactites that might remind you of jellyfish with drooping tentacles hanging from the ceiling.

the pinnacles in mulu national park in malaysian boreno sticking up into the sky
Beachmite Photography/Moment/Getty Images

Embarking on a walk above the treetops

And when you’re finally done with all things subterranean, it’s time to head 80 feet above the forest floor and walk on the canopy bridge while looking down into the shrubbery. (If you’re lucky enough to have a clear day without cloud cover, you'll even see Gunung Mulu at a distance.) Then there are the unguided walks like the Botanical Heritage Trail and the Paku Waterfall Trail that you can take at any time through signposted paths.

Meanwhile, for those who are happiest when clambering up and down vertical rocks, and cutting their own path through the dense rainforest, there are these adventure caving and trekking options, with the super popular Pinnacles trek getting booked out months in advance. This multi-day trek—the park’s website warns that it is actually more of a climb—takes you up Gunung Api to see some enormous limestone rocks with razor-sharp edges, which are collectively known as the Pinnacles.

In its inscription, UNESCO describes Gunung Mulu National Park as being “important both for its high biodiversity and for its karst (meaning irregular and sharp limestone formations) features,” and these hikes through the forest gives you a chance to see both. As is the case with the cave system itself, there are plenty of secrets within the Borneo rainforest that are just waiting for researchers and scientists—or maybe even you—to discover.

mountain facade at mulu national park surrounded by luscious green forest
Photo by Charukesi Ramadurai

What to know before you go to Gunung Mulu National Park

Best times of the year to visit

Mulu is an all-year destination but go prepared for the heat and humidity, along with sudden thunderstorms.

How to get around

Fly from Kuala Lumpur to Miri, Kuching or Kota Kinabalu in Borneo, and transfer to Maswings (a subsidiary of Malaysia Airlines) for the short flight to Mulu.

Mulu hotels & other great places to stay

Mulu Marriott Resort & Spa is worth the splurge for all its creature comforts (including a great spa to unwind in after all the hiking) in a lush rainforest setting, plus they offer a free shuttle to the park several times a day. The cheaper, if more basic, alternatives are village homestays and rooms within the park itself.

Additional helpful tips

Start with the Visitor’s Center near the main gate of the park to plan and book your excursions, since most of them have limited slots and need to be done with a trained forest guide from the local tribal communities.

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Charukesi Ramadurai is a contributor at Thrillist.