Kentucky Avenue section of Mammoth Cave

---

For reviews of all Mammoth Cave National Park tours, how to get tickets, what to wear, and rules for the tours, see the Cave Tours web page here on National Park Planner. Keep in mind that not all tours are offered year-round, and the schedule of what tours are available changes often. Be sure to check the National Park Service’s official Cave Tours web page for the current schedule.

---

TOUR OVERVIEW

The Grand Avenue Tour is one of the few tours at Mammoth Cave National Park that explores unique sections of the cave not visited on any other tour. Participants spend about three and a half hours in the cave. There are two restrooms along the route, one an hour into the tour and the second an hour and a half later.

While the Grand Avenue Tour does visit unique sections of Mammoth Cave, as with many tours, it also overlaps with the routes of other tours. It covers the entire Cleaveland Avenue, so no need to take the Cleaveland Avenue Tour if you do Grand Avenue. It also passes through the Frozen Niagara, one of the most picturesque sections of the cave, so you don’t need to do the Frozen Niagara Tour. The Domes and Dripstones Tour also visits the Frozen Niagara, but it begins at the New Entrance to Mammoth Cave, and the walk into the cave through a sinkhole and fourteen vertical domes and pits is something really spectacular. The Grand Avenue Tour does not overlap with this part of Domes and Dripstones, so if you take Grand Avenue, I certainly wouldn’t rule out Domes and Dripstones if you have the time. The Frozen Niagara is the only link between the two.

While the Grand Avenue Tour sounds fantastic, it is not for everyone. First off, three and a half hours is a long time to spend walking and standing inside a cave. Second, this is easily the most grueling of all Mammoth Cave tours. It covers four miles of cave, and the route involves climbing and ascending over 1,600 stairs as it goes up and over small mountains, which were the last things I expected to find inside a cave. To put this into perspective, the second most stair steps on a cave tour at Mammoth Cave National Park is less than 700. My thighs were definitely sore the next day, and during the tour I was sweating despite the fact that the temperature inside the cave is about 55° F.

There were two families with young children on the tour that I took. One family turned around after one mile—a Ranger had to escort them out. The other family made it all the way through, and one of their kids looked like she was only five or six years old. However, regardless of this family’s super kids, I can’t stress enough not to bring young children on this tour. I recommend kids be at least teenagers, not only because of the physical activity involved, but because they are very likely to get bored. As I said, three and a half hours in a cave is a long time for anyone.

I did just about all the tours at Mammoth Cave National Park except for the wild cave tours, and I must report that Grand Avenue is my least favorite. There are only seven stops on the tour, so it’s really nothing more than a four-mile hike through mainly large passageways of little interest. If you have done any of the tours that entered the cave at the Historic Entrance, you’ve seen how large the passageways can be. They are more like vehicle tunnels or mine shafts than anything most people associate with a cave.

Participants on the Grand Avenue Tour walk the Cleaveland Avenue passageway inside Mammoth Cave

There is some cool terrain in the slot canyons of Boone Avenue (a mile-long walk without stops), but that’s just twenty-five percent of the tour. And yes, the tour does cover the Frozen Niagara, but you can see that on the quarter-mile long Frozen Niagara Tour that takes a little over an hour.

Slot passageways of Boone Avenue inside Mammoth Cave

Furthermore, while the Ranger giving the tour provides interesting information at each stop, the topics aren’t necessarily pertinent to the location. On the history-based tours of Mammoth Cave that begin at the Historic Entrance, when the topics are tuberculosis huts or graffiti on the ceiling or an early mining operation, you are looking at it. On the Grand Avenue Tour, when the Ranger discusses animals and insects that live in the cave or gives a brief history of cave tourism, you aren’t seeing any animals or history. You are just standing or sitting down in a nondescript passageway. The same topics could be just as well discussed in the Visitor Center auditorium.

TOUR HIGHLIGHTS

CLEAVELAND AVENUE

A bus takes tour participants from the Mammoth Cave Visitor Center to the Carmichael Entrance where the Grand Avenue Tour begins. This is a manmade entrance created in 1931 so that tourists didn’t have to walk for hours from the Historic Entrance just to get to this part of the cave. After descending the staircase into the cave, the tour begins at Cleveland Avenue, a mile-long passageway with an elevator at the end.

Carmichael Entrance into Mammoth Cave

Cleaveland Avenue is very similar to the main passageway of Mammoth Cave—cavernous and without any speleothems, which is the collective term for stalactites, stalagmites, and other calcite formations most people associate with a cave. These formations require slow, dripping water to form, and a sandstone caprock covers most of Mammoth Cave, preventing water from entering. Where you do see speleothems—Frozen Niagara for example—there either is no sandstone caprock or there is a crack where water once got through (or may still be getting through today).

Beginning section of Mammoth Cave’s Cleaveland Avenue

The trail through Cleaveland Avenue is hard-packed dirt that is easy to walk on. There are a few small potholes here and there, so keep an eye on where you step.

Packed dirt trail through Mammoth Cave’s Cleaveland Avenue

While Cleaveland Avenue does not have speleothems, it does have gypsum, a white, crystal-like mineral that grows on the ceilings and walls of some dry caves when water evaporates from the rocks. Gypsum is also found in the main passage of Mammoth Cave, only there much of it was stripped off the walls by early people who came into the cave around 4,000 years ago. What they did with it, nobody knows. Most of the gypsum that remains today in the main passage is now black from the soot of torches and lanterns used to light the way from prehistoric times up through when cave tours were given before electric lighting was installed beginning in 1917.

The prehistoric people never got to Cleaveland Avenue, and while tours of this section began in the 1840s, visitation was low compared to the passageways near the Historic Entrance. This is why much of the cave walls and ceilings of Cleaveland Avenue are still covered with sparkling, white gypsum.

Gypsum on the ceiling of Cleaveland Avenue, Mammoth Cave National Park

Depending on the crack or openings in the rocks, the gypsum crystals form different shapes, some flower-like, some as large a celery stalks or deer antlers. In areas where the ceiling is low, you can get a good view of what is referred to a bouquets. Some of the curving and twisting elongated crystals look like mushroom fungus.

Gypsum crystals on the ceiling of Mammoth Cave’s Cleaveland Avenue

The most famous area of gypsum formations is the Snowball Room, which is located at the end of Cleaveland Avenue. Here gypsum grows in large clumps, as if somebody threw snowballs at the ceiling and they stuck.

Gypsum formations in the Snowball Room of Mammoth Cave

There are three stops along Cleaveland Avenue, one shortly after entering the cave, a second thirty minutes in at which point the Ranger discusses the geology of the cave, and a third at the Snowball Room where there is a restroom. There used to be a restaurant at the Snowball Room, but this closed in 2012. Some of the fixtures and a few picnic tables still remain.

Ranger stops to give a talk in Cleaveland Avenue during the Grand Avenue Tour of Mammoth Cave

Fixtures left over from the Snowball Room restaurant at the end of Mammoth Cave’s Cleaveland Avenue

The Snowball Room is 267 feet below the surface. Even so, at this point you are still 150 feet above the Green River. How can that be? Mammoth Cave is inside a mountain, so despite being hundreds of feet below the surface, you are still higher in elevation than anyone paddling down the river.

From the Snowball Room until the end of the tour, the route is paved, and any hills are climbed with the help of stairs. This is an upgraded that was completed in 2022. If you come out thinking the tour was tough, imagine how difficult it would have been without these improvements.

It was at this point that one of the families with young children turned around. Per the Ranger, the Snowball Room is the last chance for anyone to turn back.

BOONE AVENUE

One of the most unique sections of Mammoth Cave open to tourists is Boone Avenue, and it can only be seen on the Grand Avenue Tour. In fact, Boone Avenue is really the only reason to take the Grand Avenue Tour. This is a spectacular passageway created when water wore the sides of the cave smooth to form tubes and slot canyons. Similar passageways are seen in the Fat Man’s Misery section of the cave, but those are much tighter passageways with very low ceilings, requiring even average-height visitors to stoop over. In Boone Avenue, while the walls of the passageway are close together, the roof of the cave is high above. There are a few places where lower ledges jut out, so you do have to watch your head.

Narrow slot canyon passageway of Mammoth Cave’s Boone Avenue

Narrow slot canyon passageway of Mammoth Cave’s Boone Avenue

The walk through Boone Avenue passes Thorpe’s Pit. This is a vertical shaft carved by water flowing straight down into cracks in the limestone.

Thorpe’s Pit along Boone Avenue in Mammoth Cave

It is a one-mile walk (roughly 20 minutes) through Boone Avenue until the next chance to take a break, although there are no seats at the stop. There are a few stairs to climb along the way, but for the most part Boone Avenue covers level terrain.

End of the walk through Mammoth Cave’s Boone Avenue

KENTUCKY AVENUE AND MOUNT MCKINLEY

After Boone Avenue, the next long passageway is Kentucky Avenue. It is similar to Cleveland Avenue in regards to size.

Kentucky Avenue passageway of Mammoth Cave

There is a calcite formation near the start, so at one point in time water did find its way inside and dripped slowly for thousands of years to create what is known as flowstone. This is a formation that drips down the walls or over the side of a ledge.

Flowstone formation in the Kentucky Avenue section of Mammoth Cave

As I mentioned earlier, there are mountains inside Mammoth Cave—Mount McKinley is one of them. This feature, which comes towards the middle of Kentucky Avenue, is where most of the stairs are located. The walk consists of going up and over two large hills.

First steep hill in the Mount McKinley section of Mammoth Cave’s Kentucky Avenue

There are restrooms at the top of the first hill of Mount McKinley, and the tour does make a stop here.

The Grand Avenue Tour stops for a restroom break and Ranger lecture at the Mount McKinley restrooms, Mammoth Cave National Park

After the restroom break, the Grand Avenue Tour descends the first hill and then continues up an ever steeper one. The downside of the second hill descends into the Grand Canyon, which formed when one level of cave collapsed into another, creating the deep canyon-like features.

The Grand Avenue Tour continues through the Mount McKinley section of Mammoth Cave

Steep hill of Mount McKinley in Mammoth Cave

It is a twenty-minute walk from the restrooms until the next stop at the far end of Kentucky Avenue, Aero Bridge Canyon. A cable car used to operate here that carried visitors across the chasm. The cables still remain (look closely in the photo below).

Steep climb up a staircase at Aero Bridge Canyon on the Grand Avenue Tour of Mammoth Cave

Steep walls at Aero Bridge Canyon in Mammoth Cave

BIG BREAK AND GRAND CENTRAL STATION

Upon departing Aero Bridge Canyon, the Grand Avenue Tour continues through more hilly terrain, as well as terrain reminiscent of the slot canyons of Boone Avenue. Also, like in Cleaveland Avenue, gypsum is growing on the ceilings. These areas are known as Big Break and Grand Central Station.

Narrow passageways with gypsum on the ceiling between Aero Bridge Canyon and the Big Break area of Mammoth Cave

Slot canyon in the Grand Central Station section of Mammoth Cave

Twenty minutes after departing Aero Bridge Canyon, the tour arrives at the last stop before the Frozen Niagara, Fairy Ceiling. This room gets its name from a small stalactite that is forming, an indication that water is somehow getting through from the surface.

Fairy Ceiling room in Mammoth Cave

After the break, the tour ventures up one more hill to the Frozen Niagara.

Climb from the Grand Central Station section of Mammoth Cave to the Frozen Niagara

FROZEN NIAGARA

Frozen Niagara is one of the few tourist-accessible places within Mammoth Cave that has an extensive display of speleothems. It was discovered in 1923 by George Morrison. Morrison had been looking to get into the cave tourism business, and he knew that Mammoth Cave extended well beyond the boundaries of the land owned by the Mammoth Cave Estate, the trust that operated the cave at the time. He noticed that water was draining into a particular sinkhole and that cold air was coming from it, a good indication of a cave. He purchased the property in 1921 and then proceeded to blast a hole in the rocks to create an entrance. As he explored the cave, he ended up in part of Mammoth Cave that was currently being toured, so he knew his cave was connected. This allowed him to promote it as Mammoth Cave. He built some wooden stairs to the bottom and opened his New Entrance to Mammoth Cave. Two years later he discovered the Frozen Niagara.

Frozen Niagara section of Mammoth Cave

In 1926, the United States Congress passed legislation to create Mammoth Cave National Park from donated or purchased land (no seizure by eminent domain), and the government wanted Morrison’s section of the cave. At first he refused to sell, but he finally did so in 1932 for a price of $290,000. The park eventually opened in 1941 with roughly 45,000 acres.

When you enter the Frozen Niagara section of Mammoth Cave, much of what you see is flowstone. Frozen Niagara itself is a 50 foot by 30 foot section of flowstone that looks like a frozen waterfall. Cave operators promoted their tours by giving the formations within their caves spectacular, theatrical names. Because many people who came to Mammoth Cave in the early days were from the north, Morrison named the most prominent feature in his cave the Frozen Niagara, playing upon the northern tourists’ familiarity with Niagara Falls in New York.

The Frozen Niagara at Mammoth Cave is a flowstone formation

View of the Frozen Niagara from below, Mammoth Cave National Park

There is an option to take a detour down 48 stairs (and 48 back up) for those who want to journey into the Drapery Room. Drapery is flowstone that hangs from the ceiling to create curtain-like formations. You can see the sides of the drapery without venturing down the stairs, but you can’t look up into it without taking the detour. The only reason not to make the trip is that you have had your fill of stairs.

View of the Drapery Room Ceiling at the Frozen Niagara section of Mammoth Cave

Stairs into the Drapery Room in the Frozen Niagara section of Mammoth Cave

In 1924, Morrison blasted through the rocks to create an entrance that was closer to the Frozen Niagara so that he could get customers to and from it faster. The more tours per day, the more money. This is called the Frozen Niagara Entrance, and the Grand Avenue Tour eventually exits the cave through it. The bus waits outside to take everyone back to the Visitor Center.

Crystal Lake lies at the bottom of a vertical shaft near the Frozen Niagara Entrance to Mammoth Cave

The Grand Avenue Tour exits Mammoth Cave through the Frozen Niagara Entrance

Back to the Top