Researchers Map 8 New Miles of Tunnels in Kentucky's Mammoth Cave

The longest cave in the world is even longer than we thought

Mammoth Cave
Posnov / Getty Images

Spelunkers, don your headlamps. Mammoth Cave in Kentucky—the state's only national park and the "world's longest cave"—just got a little bit longer.

Most recently, surveyors from the Cave Research Foundation (CRF) have mapped 8 more miles of pathways in the system, bringing Mammoth Cave's total documented length to an astonishing 420 miles.

"THE LONGEST CAVE IN THE WORLD IS NOW EVEN LONGER!!!" the national park announced in a Facebook post on September 12.

The cave earned its "world's longest" superlative all the way back in 1969, when just 65 miles of passages were surveyed—many by the CRF. For more than six decades, Mammoth Cave has partnered with the nonprofit to explore its complex system; each year, volunteers descend into the farthest reaches of the cave to survey previously undocumented tunnels. Because lasers can't bend around obstructions, researchers must manually measure cave passages in a painstaking process.

"Every mile of cave length means that a Cave Research Foundation or Central Kentucky Karst Coalition caver physically visited and surveyed that part of the cave," CRF Eastern Operations Manager Karen Willmes told the National Park Service. "Many of the cave trips are long and arduous, involving climbing, vertical exposure, squeezes, crawlways, water, and mud. After the trip, cartographers turn the data collected on the cave trip into a map. Other volunteers provide surface support. It's a first-rate effort for a world-class cave, and we're proud to be a part of it."

Though the official Mammoth Cave map has yet to be expanded to include the newly mapped tunnels, you probably won't be able to explore them any time soon. Visits by the public are restricted to guided tours of several dozen prescribed routes, the longest of which lasts six hours and covers just 5 miles. That means there are hundreds of miles kept off-limits to visitors.

Thanks to the ongoing work of the CRF, who have put in thousands of hours of work in 60-plus years, there are plenty more tunnels waiting to be uncovered. "When it comes to discoveries in Mammoth Cave, there truly is no end in sight!" wrote the park on Facebook.