Kentucky Is Home to the World’s Longest Known Cave System — Here's How to Explore It

The area surrounding Kentucky’s Green River is lush and fertile, with miles of uninterrupted forest — but the area’s real draw lies below. Under the surface of the Earth, the brave and curious can find over 400 miles of caves, chambers, and complicated labyrinths, aptly named Mammoth Cave National Park. The giant underground wonder holds the title of the world’s longest known cave system — and if that didn’t pique your interest, the fact that entry to the park is free, just might.

Kentucky’s impressive cave system has been an area of interest for centuries. Mammoth Cave boasts over 400 miles of surveyed passageways making the site nearly twice as long as the second-longest cave system: Mexico’s underwater Sac Actun cave.

Mammoth Cave was described by one of the site’s early guides, Stephen Bishop, as a "grand, gloomy, and peculiar place.” The system includes vast chambers and complex labyrinths that take visitors over 300 feet below the surface of the earth to a sunless and space-like landscape.

While the park is free, tickets are required to enter Mammoth Cave. Professional guides offer daily tours that range from $6 to $60. Guests can book the Domes and Dripstones Tour to go on a journey through the cave’s dripstone formations for $17 or take the Gothic Avenue Tour for $15 to see the cave’s historic entrance and view markings from 19th-century visitors who wrote using candles.

Reservations to Mammoth Cave National Park are not required, but are strongly recommended as cave tours frequently sell out. To reserve your spot, visit the park's website..