Join this project to support backcountry trail maintenance in Mammoth Cave National Park, and in your free time, explore the longest known cave system in the world! Mammoth Cave National Park is a park on two levels – 52,830 acres of reclaimed hardwood forest and winding riverways, and below it, the longest known cave system in the world, surveyed at 426 miles to date. Located within a day’s drive of major population centers, it offers camping, hiking, horseback riding, bicycling,…