Sinkhole Trail in Mammoth Cave National Park

Length:  1.1 mile (one way)
Time:  45 minutes
Difficulty: Moderate with a few short-but-very-steep hills

The Sinkhole Trail (aka Mammoth Dome Sink Trail) is a 1.1-mile out-and-back trail with its northern trailhead near the Mammoth Cave Visitor Center and its southern trailhead at the intersection with the Echo River Spring Trail near the Green River Ferry. I started at the Visitor Center and added the wheelchair-accessible Echo River Spring Trail (which makes a loop) to the hike, then returned to the Visitor Center on the Whites Cave Trail. There is no reason to hike out-and-back on the Sinkhole Trail.

Sinkhole Trail map (click to enlarge)

To get to the northern trailhead you must first walk a short distance on the Heritage Trail. This begins at the Mammoth Cave Lodge, which is on the other side of the footbridge at the rear of the Visitor Center. Follow the boardwalk for a tenth of a mile until coming to a Heritage Trail information board. This is the start of the loop portion of the trail. Stay to the left (not the path to the motel), and just up ahead is the start of the Sinkhole Trail. A sign refers to it as the Mammoth Dome Sink Trail.

Intersection of the Sinkhole and Heritage trails near the Mammoth Cave Visitor Center

The Mammoth Cave Visitor Center is high above the Green River, and since the Sinkhole Trail ends at the river (or close to it), it should come as no surprise that the majority of this hike is downhill. However, it starts off as a smooth dirt path that covers level ground for .15 mile. It passes a small building that functions as a pump station. Wastewater from the Visitor Center, Lodge, and Mammoth Cave Campground are collected here, then pumped to Park City for treatment. This keeps the wastewater from flowing into the Green River.

Typical terrain at the northern end of the Sinkhole Trail in Mammoth Cave National Park

Wastewater pump station near the Mammoth Cave Visitor Center

The Sinkhole Trail soon comes to an intersection with a trail that heads down a hill to the left. According to a directional sign, 100 feet straight ahead is an overlook of the sinkhole. However, there is no longer a view due to excessive vegetation, so don’t bother. Take the left to continue the hike. While not identified on the sign, this is the Sinkhole Trail.

Left turn for the Sinkhole Trail prior to the sinkhole overlook, Mammoth Cave National Park

The first of three downhill segments of the Sinkhole Trail now begins. The hill is .2-mile long and has a very brief level reprieve about a third of the way down. The first part of the hill has an average grade of 11% (15% is where strenuous hiking begins). The second half has an average grade of 13%. The trail follows along a ridge, so there is a steep drop off on one side and a steep bank on the other. The trail also has a fair share of rocks and roots on the surface, so it’s not as easy hiking as it was at the start.

Typical terrain on the first downhill section of the Sinkhole Trail when starting from the Heritage Trail at Mammoth Cave National Park

On the way down is an interesting area full of large boulders. A wayside exhibit informs that just 70 feet below is Lookout Mountain in Rafinesque Hall, a section of Mammoth Cave.

Area of the Sinkhole Trail directly above Lookout Mountain in Rafinesque Hall, part of Mammoth Cave

At .4 mile into the hike is a short trail that leads into the Mammoth Dome Sink, the sinkhole that gives the trail its name. It is very steep (20% grade) and 150 feet in length, and of course you must climb out of the hole to get back on the trail. A wayside exhibit explains the geology of the sinkhole.

Short trail leads from the Sinkhole Trail to the Mammoth Dome Sink, Mammoth Cave National Park

The Mammoth Dome Sink, which today is a large depression in the earth’s surface, led to the creation of the Mammoth Dome. Water typically does not penetrate the sandstone layer that lies just below the surface, but in this case cracks formed in it and water seeped into the soft limestone layer underneath. After millions of years this water created a cavity that eventually collapsed to create a sinkhole. Water that collected in the sinkhole continued to drain into the limestone, and eventually a 192-foot vertical shaft was created—Mammoth Dome. The shaft and the sinkhole are not on top of each other, so chances of them one day connecting to form a much larger sinkhole are remote.

Illustration of the Mammoth Dome Sink and the Mammoth Dome

If you have taken a tour of Mammoth Cave that began at the Historic Entrance, you may have exited the cave by climbing a tall fire tower at the end of the tour. That fire tower is inside the Mammoth Dome.

Fire tower inside Mammoth Dome, Mammoth Cave National Park

In truth, reading the information on the wayside exhibit is more interesting than actually hiking into and out of the actual sinkhole, which is nothing more than a large gully. My advice is to skip the detour if for no other reason than to save time.

Mammoth Dome Sink along the Sinkhole Trail in Mammoth Cave National Park

Just beyond the sinkhole is the intersection with the River Valley Trail, which forks off to the right. Follow the directional sign to WHITES CAVE and ECHO RIVER to stay on the Sinkhole Trail.

Directional sign near the intersection of the Sinkhole and River Valley trails in Mammoth Cave National Park

Beyond the River Valley Trail intersection is a .3-mile segment of the Sinkhole Trail that heads down and out of a shallow valley. Both the descent and ascent are mild and may well go unnoticed if you aren’t paying attention. The trail’s surface is now quite smooth, making this part of the Sinkhole Trail an easy hike.

Typical terrain on the Sinkhole Trail south of the intersection with the River Valley Trail, Mammoth Cave National Park

At .8 mile into the hike is White’s Cave. The entrance is blocked, but if you want to see it, it’s just a stone’s throw from the trail.

White’s Cave stop on the Sinkhole Trail in Mammoth Cave National Park

White’s Cave in Mammoth Cave National Park

Just past the cave is the intersection with the Whites Cave Trail, the trail I used when returning to the Visitor Center. Take a right to remain on the Sinkhole Trail.

Intersection of the Sinkhole and Whites Cave trails, Mammoth Cave National Park

From the Whites Cave Trail intersection, it’s pretty much downhill for the last .3 mile of the hike. There are a half dozen very short segments with very steep grades (up to 30%), with the most difficult coming along the last tenth of a mile. The trail also gets a lot more rocky, so watch your step.

The Sinkhole Trail heads downhill south of the Whites Cave Trail intersection, Mammoth Cave National Park

Typical terrain on the section of the Sinkhole Trail between the Whites Cave and Echo River Spring trails in Mammoth Cave National Park

The Sinkhole Trail dead ends into the paved Echo River Spring Trail. At this point you can hike the enjoyable .7-mile loop or head back the way you came. I do suggest returning on the Whites Cave Trail just so that you don’t see the same things twice. It is similar in difficulty to the Sinkhole Trail, though this time the hike is mainly uphill to the Visitor Center.

Intersection of the Sinkhole and Echo River Spring trails, Mammoth Cave National Park

Southern trailhead for the Sinkhole Trail in Mammoth Cave National Park

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