Located in a 100-acre former limestone quarry, Louisville Mega Cavern is a 17-mile manmade underground cavern that is now home to the world’s only underground zip line. The new MegaZip experience includes five different zip lines (including a dual racing zip line) that whip you along at 70 feet above the cavern floor. The two-hour zip tour also includes three suspension bridges that will test your balance as well as your courage.

For those who prefer a tamer adventure, the 70-minute historic tram tour teaches participants about the geology and green building technology of the cavern, which is home to the largest recycling center in the state. One of the highlights of the tour is the worm recycling/tasting room, where European night crawlers, scientifically engineered to speedily consume paper products, display their composting expertise. Here, you’ll witness your guide demonstrate his or her night crawler nibbling skills, and you’ll get an opportunity to slurp down a slimy snack yourself. The tram tour also covers the cavern’s history, including how it was designated as a fallout shelter during the 1960’s Cuban Missile crisis.

During the summer, Mega Cavern’s constant 58-degree temperature makes it a perfect place to beat the heat. And in November and December, the tram tour is closed to make room for Lights Under Louisville — the world’s only underground holiday light display.