At our tour guide’s mention of scorpion spiders, an uneasy murmur rippled through the crowd.
We were about to enter the labyrinth – a twisty dark corridor that weaves through part of the Camuy River Cave Park, a gigantic cave system in northern Puerto Rico. Large arachnids call this part of the cave home, and as my fellow adventurers and I felt our way through the blackness, I noticed a shadowy spot on a cave wall.
As I squinted more closely, an arachnophobe’s nightmare came into focus: A spindly, fist-size scorpion spider – technically called a tailless whip scorpion – clung to the rock, sporting a set of long, spiny pincers. Actually neither scorpion nor spider, the animal looks fearsome enough for both monikers but is harmless to humans. My boyfriend, Brian, and I examined it by the glow of our iPhones, fascinated by this unique cave dweller.
Perhaps the largest of Puerto Rico’s hundreds of caves, Camuy quickly captures you in its web of wonders. Rio Camuy, an underground river that’s been carving out the nearly 11-mile-long cave for millions of years, still roars beneath your feet, and the park’s “show” cave, Cueva Clara, or Clear Cave, is awe-inducingly enormous, with a ceiling about 17 stories high and hundreds of feet wide. Camuy – and much of northern Puerto Rico – is part of a karst geological formation, which consists of rocks easily eroded by water, such as limestone.
Considering how impressive the site is, it’s surprising that scientists explored the cave for the first time only in the 1950s. (Archaeological evidence shows that prehistoric Taino people had visited the cave over the centuries.) In 1986, the area became the 300-acre Camuy River Cave Park, a protected area of the Puerto Rico commonwealth that offers guided walks to tens of thousands every year.
As nature addicts, Brian and I decided to swap sun and sand for the subterranean and visit Camuy during our week-long trip to Puerto Rico in November. Heeding multiple warnings that the cave can close by noon due to rain or crowds, we rented a car early in San Juan and got to the park by midmorning, just in time to jump on the orange tram that ferries tourists to the cave’s southern entrance.
Chugging downhill through a misty rain forest, I soaked in the green riot of lilies, ferns, vines and moss-covered trees – a very Jurassic Park experience, as a visitor described it later. We got off the tram and our guide, Jarliann Rodriguez Sanchez, walked our large tour group down a path, at the end of which I expected to enter the cave via a narrow passage. Instead, as we rounded the turn, the earth literally yawned open, showcasing a humongous cave, like curtains pulled back on a theater stage.
We took stairs down into the belly of the cave, staring upward at the ceiling, which was rounded like a hollowed-out pumpkin and studded with a thick row of stalactites – mineral formations that grow from cave ceilings like icicles. Stalagmites, in contrast, rise up from the bottom of a cave as water drips down. On another cave tour years ago, I’d learned a simple way to remember the difference between the two common cave sights: A stalactite holds “tight” to the ceiling.
Farther into the dimly lit cave, the temperature dropped into the 60s, and the sound of chirping cave crickets and dripping water bounced off the walls. High above us, bats – possibly the Jamaican fruit bat, one of the cave’s resident species – swooped from roost to roost, among the thousands of the flying mammals that live here. The cave had a reverential feel to it, sort of like being in Rome’s Pantheon. But instead of wondering how ancient Romans had built such a perfectly shaped dome, I was thinking about how the Rio Camuy had shaped such beauty over the millennia; experts believe that the cave is a few million years old.
“I just got a giant cave kiss,” Brian said behind me, using the cavers’ term for a drop of water that falls on your face.
Walls and ceilings
Sanchez began pointing out the cave’s various rock formations, which water and time had shaped into a human face, an elephant ear, a head of broccoli, a giant muffin and, for fans of “Pirates of the Caribbean,” Davy Jones. She was also constantly reminding us to “use your imagination” to come up with our own interpretations: I thought that the black stalactites on the ceiling looked like a straggly beard.
Sanchez told us that many of the formations are still growing, ever so slowly, and that there are no plants in the cave – the only green stuff you'll see is the moss sprouting near the artificial lights that help tourists see the cave. I learned later that the cave does host some hardy fungi, though.
Our group chuckled when Sanchez shone her laser on a strip of “cave bacon,” a type of formation created when mineral-rich water runs down a wall, hardening over time into what looks like wavy bacon.
A cliff and a sinkhole
We followed the curving, sometimes slippery path through the cave out of its northern entrance, which is framed by long stalactites that hang over the opening like locks of hair. Before us towered a tall, lush cliff, and we peered over the edge of a platform more than 400 feet down to the Espiral, or Spiral, sinkhole.
Such features are common in karst regions and mostly occur when underground water erodes soluble bedrock for a long time, creating a depression. Occasionally, though, they form when a cave roof collapses in on itself. Thirsty vines stretched toward a pool of muddy river water at the bottom – a very different Rio Camuy from the one we saw a few minutes later in the labyrinth, where a violent rush of water surged deep below, a reminder of the forces that made the cave. Sanchez also pointed out stains of brown bat guano – otherwise known as poop – on the cave walls. Surprisingly, it’s an ingredient of gunpowder, she told us.
After we left the cave, I asked Sanchez about her experiences with whip scorpions. She showed me a picture on her phone of one of the arachnids chowing down on a cave cricket, its preferred prey. She also told me about other animals she’d seen in the park, such as snails, spiders and snakes.
Making its way back uphill, our tram made one last stop: at an observation platform overlooking the Tres Pueblos – or Three Towns – sinkhole, which, at about 400 feet deep and 650 feet wide, is big enough for one of San Juan’s historic forts to fit into. Most of the giant crater’s gray limestone walls were covered with thick vegetation.
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