The Steepest Trail in the World? An Insane Hike in the Rainforest with Venomous Vipers and Headhunter Tribes - The Pinnacles in Gunung Mulu National Park in Borneo
Last year on our Southeast Asia trip we went and explored one of the coolest and wildest places I’ve ever been. Gunung Mulu National Park, which is only accessible by air or boat and situated on the island of Borneo. The island is divided into three countries, Malaysia, Indonesia, and Brunei. We visited the Malaysian area of Borneo.
Colossal Caves of Gunung Mulu
See the tiny people in the middle left of the picture for scale.
Nestled in the lush rainforests of Malaysian Borneo on the island's northwestern edge lies one of the world's great geological wonders - the caverns of Gunung Mulu National Park. This UNESCO World Heritage Site contains some of the largest underground passages and chambers on the planet formed over millions of years by erosion.
The gaping maw of Deer Cave looms before us, a towering 174-meter opening in the hillside that beckons with its foreboding darkness. As we approach with our headlamps illuminated, the sheer scale of this geological marvel begins to become apparent.
"This isn't just a cave," our guide explains over the thunderous rush of the nearby river. "Deer Cave is considered the largest single cave passage in the entire world."
We stand in awe, straining our necks to take in the full proportions of the opening dwarfing our group. When he tells us the passage is over 2 kilometers long and up to 170 meters high inside, it's almost incomprehensible. Steeling our nerves, we clip on our headlamps and venture within.
The transition from the thick Bornean rainforest into Deer Cave's eternal gloom is jarring. One minute we're surrounded by dense jungle, the next we're standing in an immense, silent grotto of carved rock walls disappearing into blackness in every direction. Our headlamps can barely penetrate the oppressive shadows.
As our eyes slowly adjust, faint details begin to emerge from the murky depths. Shadowy outlines of rock ridges, towers and needles higher than city buildings materialize, seeming to defy gravity. These aren't just humble cavern decorations, but gargantuan petrified waterfalls sculpted by nature over millions of painstaking years, eerily frozen in perpetual suspended animation in the subterranean gloom.
As we venture deeper into the silent shadows of Deer Cave, our headlamp beams begin picking up strange flittings in the blackness ahead. Hundreds of tiny eyeshines spark to life like demented fireflies frozen in the void.
"Those are the bats," our guide whispers reverentially. "Millions of them roost in here during the day before their nightly exodus."
We can make out the tangled, furry masses clinging to every nook and crevice overhead. The wrinkle-lipped free-tailed bats seem to coat the cave ceiling in a crustaceous layer, their bodies packed together so tightly it's hard to distinguish individuals.
The Bat Exodus
As the tropical sun begins to dip in Gunung Mulu's rainforest, we position ourselves at the gaping mouth of Deer Cave in eager anticipation of the extraordinary nightly ritual about to unfurl. Just before dusk, the first telltale signs emerge - the faint rustling of millions of tiny flapping wings.
Over the next two to three hours, this rustling builds to a crescendo as more and more bats emerge, forming a pulsating, twisting vortex of black bodies streaming out endlessly. The rapid fluttering and whooshing of wings is clearly audible from thousands of feet below the exiting bats.
At the peak, experts estimate a staggering 3 million wrinkle-lipped free-tailed bats pour out of Deer Cave's interior. The sheer numbers are incomprehensible, with great spiraling clouds of bats covering the sky above.
While their numbers are staggering, the nightly exodus also reveals remarkable coordination. Rather than a frenzied free-for-all, the bats form sophisticated cylindrical patterns, constantly shifting position in an intricate dance to avoid predation. Their twisting, almost geometrically-precise configurations allow individual bats to cycle from the edge to the center to avoid being plucked off by bat hawks and falcons waiting patiently nearby.
Watching and hearing this bat exodus at Gunung Mulu is one of the most memorable moments of our lives. A visceral reminder of the immense scale and complexity of the natural world.
The Pinnacles 3D 2N Hike
Day 1: To reach the trailhead for the Pinnacles, we took a longboat up the Melinau River deep into the jungle interior of Gunung Mulu. The ride was bumpy but scenic, with limestone cliffs rising on either side. After 4 hours, we arrived at the trailhead to Camp 5 - a basic campsite with shelters and cookhouses. That was as far as we could go by boat. It was a relatively easy and mostly flat 9km hike to reach Camp 5.
We got caught in a rainstorm 1km out from camp. The storm came out of nowhere and sounded like a freight train as it came. We stopped and listened, asking each other, “Is that a plane, or what is it?” Turns out it was the wind driving the sudden thunderstorm.
A German couple hiking behind us got caught in a tree-fall during the storm; the woman got knocked to the ground by a large tree and twisted her ankle. Call it good luck that she didn’t get hurt more or bad luck that a tree fell on her; either way, it was a scary incident that showed the dangers and unpredictable nature of the Borneo jungle.
Day 2: An early 5am wakeup call jolted us from our sleep. We needed to summit the Pinnacles by mid-morning before intense heat set in. The trail started with a grueling series of wooden staircases ascending root-tangled slopes. I was already drenched in sweat after 5 minutes of climbing.
The terrain grew increasingly precipitous and exposed as we gained elevation. Thick ropeways assisted our ascent up near-vertical rock faces and muddy chutes. Our guide warned us to watch our footing - a slip or misstep could be disastrous on such treacherous ground.
After 3 hours, we reached the final gut-punching stretch - a series of aluminum ladders and ropes leading straight up. There were 17 ladders strung along this section crossing over precipitous drop-offs and deep ravines.
The climb to reach The Pinnacles took 4 hours and in that time we climbed 1,200 meters and covered only 2.4km of linear distance. The iconic limestone formations are featured on the $50 bill in Malaysia. Climbing down was even worse than the way up, having to retread the same precarious path. In total it took about 7.5 hours to make the 4.8km round trip hike and our legs were jelly by the end.
Our guide, Suki, would go on to make this same climb 3 more times that week. He said he would sometimes run back down the trail - it seems impossible to me given the steep grade but I believe him.
