The cave is only open through guided tours, according to the National Park Service, even though entrance to the park is free. Reservations are encouraged, but tickets are also available on-site.

Reservations: 800-967-2283. The Mammoth Cave Hotel (270-758-2225, www.mammothcavehotel.com) is near the park visitors center and offers options ranging from hotel rooms to cottages.

Discover Mammoth Cave and hidden summer hikes in Kentucky. Read tips on top trails, cave tours, planning advice and secret paths for a perfect getaway.

Mammoth Cave is located about 30 minutes outside Bowling Green, Kentucky by car. According to the park’s website, prehistoric seas deposited limestone in the area around 325 million years ago.