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| Flowstone at Frozen Niagara. Photo courtesy of Mammoth Caves NPS. |
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| Cave map, courtesy Mammoth Cave NPS. |
Grand Avenue Tour runs 4 miles at Mammoth Cave
Day hikers can explore the world’s longest known cave system on the Grand Avenue Tour at Mammoth Cave National Park.
More than 400 miles of explored caves sit beneath the surface of southcentral Kentucky. The National Park Service offers a variety of tours of the caves, but perhaps the best – and certainly the most physically demanding – is the Grand Avenue Tour. It covers four miles with 700 stairs along the way; because of this, children must be at least six years old to go on the hike.
To reach the trailhead, from Interstate 65 take Exit 48 in Park City, Ky. Travel north on Park City Road/Ky. Hwy. 255. Turn left/northwest onto Mammoth Cave Parkway/Ky. Hwy. 70. The parkway splits from Hwy. 70; at this split, follow the parkway right/north to the visitor center. From there, a bus transports you to the Carmichael Entrance.
Not a natural entrance, it was blasted open during the 1920s. The trail starts with a walk of nearly 200 steps down. Among the first sights is the Rocky Mountains, which are tall piles of broken rocks.
Snowball Room
From there, the tour enters a mile-long section known as Cleaveland Avenue. Elliptical in shape, the walls are encrusted with white gypsum that forms interesting, flower-like shapes.
Next up is the Snowball Room where hikers can dine underground and use restrooms. Located 26 stories below the surface, the gypsum on the ceiling forms round shapes reminiscent of snowballs.
After the break, hikers enter the section known as Boone Avenue, a narrow, twisting passageway carved by water. Among the geological features are Mary's Vineyard, Thorpe's Pit (named for athlete Jim Thorpe), the Rock of Gibraltar, Alice's Grotto, and the Grand Canyon.
Following the passageway is a hilly section called Kentucky Avenue. The rough terrain is due to rock fall from the cave roof. Among the highlights is Mount McKinley, which at 19 stories below the surface is the highest point of the fallen rock hills. Restrooms also can be found nearby.
Frozen Niagara
Next comes the wide open room nicknamed Grand Central Station and then Frozen Niagara, which at 130 feet below the surface is the cave’s most famous rock formation. Frozen Niagara consists of a flowstone formation and stalactites draped over layered limestone.
Nearby sights are the Drapery Room, the deep pit known as Crystal Lake, and Moonlight Dome. The tour ends at the Frozen Niagara Entrance with a bus taking hikers back to the visitor center.
Mammoth Cave has long been a popular destination. Humans first entered the cave system at least 4000 years ago, and modern tours have been given since 1816. These days, though reservations are not required, they are highly recommended and cannot be made the same day of a tour.
Also note that there are a number of cave restrictions. Among them: No strollers, child carriers, large trekking backpacks, or flash photography are permitted on the tour.
Learn about other great America national park sights in my Best Sights to See at America’s National Park guidebook.
