Mammoth Cave National Park in central Kentucky is home to, by far, the longest cave system in the world. There are 405 miles of discovered cave tunnels within Mammoth Cave National Park, a distance that is two times as long as the second-longest cave system in Sac Actun, Mexico.
A cave of this caliber takes millions of years to develop, and the geology of the Kentucky region contains the perfect conditions for such a cave to form. Kentucky is known as a karst landscape, an area of land where water moves rapidly underground and dissolves rock. As rainwater and snow fall to the ground, they bond to carbon dioxide, which makes the water slightly acidic. The acidic water works its way through the soil and and begins to slowly dissolve the limestone rock that is so common in the Kentucky region, forming sinkholes (which are found by the hundreds in this region) and caves.
Soluble limestone rock is common in cave systems throughout the world. An insoluble sandstone roof makes Mammoth Cave unique and special. The insoluble sandstone protects the limestone below it, keeping the cave very dry from the rainwater seeping through the soil. The dry environment of the cave explains why there are no calcite flowstone formations. On the other hand, the dryness of the cave does allow for delicate gypsum formations, which are extremely rare and beautiful. In addition, beautiful stalagmites and stalactites grow where the sandstone roof has eroded and allowed water to interact with the limestone.
Over thousands of years, the dissolved rock begins to open up small crawl-ways. Over millions of years of limestone erosion, huge passageways and rotundas begin to appear. On ranger-led tours of the caves you will have the opportunity to see both of these amazing geological phenomena.
Certain cave tours are only available during specific seasons of the year. Be sure to check with the National Park System online or by calling the visitor center in order to see which cave tours are available. Reservations are not required for these tours, but they are strongly recommended because they can fill up very quickly. All requests for reservations must be made two weeks in advance of your anticipated tour date.
Strollers, tripods, flash photography, and all child backpack carriers are not allowed on the cave tours unless noted otherwise.
There are many ranger-led activities that do not go inside the caves. Birdwatching, wildflower education, coffee with a ranger, heritage walks, and ranger-led hikes are just some of the many opportunities for ranger-led experiences in the park. The rangers are full of helpful information that extends far beyond their beautiful cave system.
In addition, there are about 84 miles of trails in the park. These trails are mostly used for horseback riding and hiking, but there are also designated trails for mountain biking. The Green River, located in the park, is a popular place to go kayaking, canoeing, boating, and fishing.
The Buffalo Creek + Sal Hollow Loop is a particularly popular trail that is filled with waterfalls, massive sinkholes, creek crossings, and wildflowers.
The park offers many camping opportunities. There are three developed campgrounds and over a dozen primitive backcountry campsites that are located either in the woods or by the Green River. Backcountry camping requires a permit, which can be obtained for free in the backcountry permit office in the park's visitor center.