Hiking Underground at Mammoth Cave National Park

In the South, there’s no better time for an underground hike than the middle of summer. When August temperatures above ground make even the most heavily shaded trails feel like saunas, Tennessee and Kentucky offer several optimal underground hiking alternatives. None of these is more well known than Mammoth Cave National Park, easily accessible by a ninety-minute drive north from Nashville. As the only national park that’s justifiable as a day trip from my home in the Music City, the fact that I didn’t explore this place sooner completely baffles me. However, I couldn’t have picked a better opportunity to reunite with one of my favorite hiking partners and beat the heat by taking this chapter in the second iteration of my New Year’s Resolution underground.

Naturally, Mammoth Cave has been high on my “unexplored hiking destinations within a couple of hours of Nashville” bucket list (yes, I’ve got one of those) since the beginning of this journey in January of 2018. But this local climate that’s nothing short of smoldering for about eight months every year, as I’ve since learned, significantly changes beneath the earth’s surface. My hike at Mammoth Cave with Megan, a close friend who I’ve hiked with more times than maybe anyone, felt different than any other hike I’ve ever taken, and not just because of temperature differential below ground. I’ll admit that part felt so refreshing, because I can’t think of another summertime activity (outdoors and out of water) this close to home that gives me the chills, in the best way.

The entirety of the four-mile trail that Megan and I hiked lay beneath the ground. However, I’d describe this trail as generously moderate, for a number of reasons. First and foremost, the National Park Service does not allow mere mortals to explore Mammoth Cave without a guide. I respect this, since Mammoth Cave is the world’s largest known cave system. The cave encompasses more than 400 miles of explored passages, only 14 of which are accessible to the general public, and many experts believe that at least half of the Mammoth Cave system has yet to be discovered. To the federal government, that translates to countless opportunities for unaccompanied and inexperienced tourists to get lost in the dark. As if NPS needs an additional reason to require Mammoth Cave visitors to enter the cave with a guide, it’s also extremely hazardous for the cave’s internal ecosystem to endure the human impact associated with unmitigated foot traffic.

Accompanied by two park rangers and sixty other cave visitors, Megan and I descended into Mammoth Cave and embarked on the Grand Avenue Tour, the longest and most strenuous option available that doesn’t require caving equipment or experience. If you’re planning to visit Mammoth Cave, check out their website to learn about your tour options, as many (including Grand Avenue) are only offered seasonally. Megan and I were lucky to snag two of the last remaining spots on our tour about a week in advance. All tours require check-in at the Visitor Center prior to departure via shuttle to one of a handful of cave entrances.

Soon after entering the cave, I began reaching into my backpack for my pullover jacket, as the temperatures inside the cave felt at least forty degrees cooler than those above ground. Besides the chill in the air, the first thing I noticed was the infrastructure built within the cave, thoughtfully designed to accommodate crowds who don’t spend much time underground. The trail was smooth and even, and actually paved with a concrete mixture made from loose rubble cleared from the cave’s passages that are now accessible to visitors. The cave also had electricity, powered by generators along the trail that the enabled the rangers to turn lights on and off as we moved from one area to the next. Ladies and gentlemen, this cave even had bathrooms, and not the portable kind. These toilets flushed.

All things considered, this might be the most civilized hike I’ve ever taken. It’s certainly the largest group I’ve ever hiked with, and the first guided hike I’ve taken since I started this journey. Although part of me feels disheartened about the manmade modifications to such an astounding natural wonder, another part of me appreciates that the National Park Service has made it possible for people like me to safely explore a place that would otherwise be inaccessible. This managed approach grants access to a limited number of guests and only in predetermined areas, all for a price. The controlled nature of this organized system, and the revenue that it generates, helps to preserve the cave for future generations of explorers.

Ranger Steve, the NPS officer who led our journey, provided detailed historical and speleological anecdotes as we moved through the caverns. Speleology is the term that defines the study of caves, and I learned the name of this ancient science through a wise sage called Google. While most of the passages that we moved through didn’t feel cramped at all, this journey included a few spaces that would make a claustrophobe sweat, even in the cool subterranean climate. The rock formations changed as we moved through the cave, and Ranger Steve provided an excellent translation of the story that unfolded through the intricate patterns on those limestone walls. Mammoth Cave developed over the course of hundreds of millions of years, and it’s still a magnificent work in progress.

As my first underground hike, this one will always stand out in my memory as a completely unique experience, and one that I’m so grateful to have shared with my favorite Kentucky native, Megan. Not surprisingly, hiking through dark spaces beneath the earth’s surface produces sub-optimal lighting for photos, and NPS has a strict policy against flash photography in the cave, due to its harmful impact on bats, spiders, and the other species that call Mammoth Cave home. If you’re looking for a hike that will produce an array of likable photos to post on Instagram, this destination isn’t for you. I think that’s part of the appeal. Mammoth Cave presents a rare opportunity for the average tourist to explore one of the world’s most impressive natural phenomenons. There are no mountain vistas or breathtaking waterfalls inside this cave, but that doesn’t compromise the beauty of this enigmatic landscape.

Caves feel so personal to me, because of the closeness of the surrounding landscape, both comforting and intimidating at the same time. Despite the fact that I hiked through Mammoth Cave as a member of a large tour group, parts of this experience felt incredibly intimate. I salute NPS for this. While I still prefer adventures above ground, I foresee additional cave hikes in my future, and I’m lucky to live in an area that provides plenty of subterranean options.