The essential guide to Kentucky's Mammoth Cave National Park

A mossy rock overhang on the Cedar Sink Trail in Kentucky's Mammoth Cave National Park. Photo / 123RF

Home to the world's longest known cave system, Kentucky's only national park is a must-visit for keen spelunkers.

As the USA's National Park Service celebrates its centenary, we're profiling the wilderness areas it manages.

Today: Kentucky's sole national park . . .

Mammoth Cave National Park

"No changes of seasons, no sound of storm or thunder penetrate here; winter and summer, day and night, peace or war, it is all one; a world beyond the reach of change, because beyond the reach of life."
- John Burroughs, naturalist, 'In Mammoth Cave' (1887)

In a state known for its elevated landscape in the form of the Appalachian and Cumberland mountains, it is an inverse topography — the world's longest known cave system — that is Kentucky's lone national park. This underground wonder, whose dimensions suit its name, is mapped at 644 kilometres — a length that increases with ongoing exploration.

Here, midway between Louisville and Nashville, this limestone labyrinth with a colourful and contentious (land-ownership) past fascinates visitors.

The deep history goes back 10 million years in time and 115 metres into the earth, where ancient human remains and artefacts are legally protected.

The modern story includes African-American history, such as the legacy of Stephen Bishop, who ventured into unexplored areas and became a guide. He is buried at the park's Old Guides' Cemetery.

In popular culture, Mammoth has inspired a short story, an early computer game, poetry and rock-music lyrics.

Inside a cavern at Mammoth Cave National Park. Photo / 123RF

Today, park rangers continue to guide cave visitors through tours of varying length, style and level of physical demand — from easy to extremely strenuous. Tours include Gothic Avenue, which has historically significant passageways where 19th-century signatures are preserved.

Interior temperatures average about 12 degrees. Bring a jacket or sweater and wear shoes suitable for walking. Aboveground activities include hiking and fishing.

Size: 52,830 acres

Founded: 1941

Attendance: 2 million entire park; 566,895 cave tours (2015)