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Trail Guides

Exploring the Caves & Old Growth Forests Along Trail 3 of Spring Mill State Park, Indiana

Guide to hiking trail three in spring mill state park indiana


Of the 8 hiking trails in Spring Mill State Park which take you on a unique adventure through some of the varied terrain of the park, Trail 3 is by far the crowd favorite. Aside from the area surrounding the fully restored pioneer village, this is the most visited part of the park. Trail 3 has a little bit of everything to keep sightseers occupied with its thousands of sinkholes, 300 year old virgin timber forest, and of course the three main caves which attract visitors with a seasonal underground boat tour. While visiting Spring Mill State Park during the main season will require an entry fee of $9 per car, coming here during late fall through early spring will get you into the park for free. Boat tours are seasonal and operate from Memorial Day through October.

Trail 3 | 2.5 Mile Loop

Spring Mill State Park Location | Google Maps

Spring Mill State Park Trail Map

Regularly voted as one of the Top 5 Best State Parks in Indiana, Spring Mill State Park draws nearly a million visitors each year. This 1,358 acre park boasts an incredible array of recreation opportunities from touring a fully restored 1800’s pioneer village to horseback riding, cave tours, mountain biking, fishing, and hiking. One of the best trails to hike here which showcases the true beauty and uniqueness of the topography is Trail 3. This 2.5 mile loop travels through three dedicated nature preserves; Donaldson Cave, Mitchell Karst Plains, and Donaldson Woods, which contains the third largest stand of virgin timber in Indiana. Along the path the trail contains stops at three of the parks largest navigable caves; Twin Caves, Bronson Cave, and Donaldson Cave. 


twin caves boat tour and trailhead in spring mill state park and Mitchell Karst plains nature preserve Indiana

Twin Caves (Upper Cave)

I planned a visit here during early spring as this park is noted for having an incredible wildflower display, especially in the areas containing old growth forest. With the intention of focusing my afternoon on mainly hiking Trail 3, I headed on over to the Park Office next to the Grissom Memorial to pick up a park map, ask the rangers for some suggestions, and to get my bearings dialed in. Trail 3 coincidentally has 3 separate trailheads along its 2.75 mile route; one at Donaldson Cave, Twin Caves, and Spring Mill Inn. While there is no bad place to start, I chose to begin my journey at the Twin Caves and Bronson Cave trailhead.


twin caves in Mitchell Karst plains nature preserve within spring mill state park Indiana

While Spring Mill State Park was established in 1927, the idea of setting aside this land in order to conserve it originated nearly a hundred years prior to that. As a native Scots, George Donaldson was drawn to the karst region of Indiana in 1865 by the allure of cave exploration. Considered an eccentric adventurer, Donaldson traveled throughout North America accumulating vast estates of natural land, each selected for its beauty.  After a day spent wandering the property, he put in a bid to purchase the first of 180 acres that would eventually become Donaldson Cave and Donaldson Woods Nature Preserve. This new estate of his would come to be known as, “Beautiful Shawnee”.


upper cave entrance of twin caves of Mitchell Karst plains nature preserve within spring mill state park Indiana

From the parking lot, its a straight shot down into the ravine of Twin Caves. Walking down the newly built wooden staircase, you can still catch a glimpse of the original stone steps erected by the Civilian Conservation Corps in the 1930’s. It often shocks visitors unfamiliar with karst landscapes to know that this adorable little river valley they’re walking into is actually a huge sinkhole. Upper and Lower Twin Caves are part of the much larger Shawnee Cave System. The cave system, which extends outside of the park, begins at the Sinks of Mosquito Creek in the present day Shawnee Karsts Preserve. In 2012, the Indiana Karst Conservancy purchased the 80 acre property adjacent to Spring Mill State Park in order to protect the entire length of the 8,000 foot cave system and its watershed. 


lower cave entrance of twin caves in Mitchell Karst plains nature preserve within spring mill state park Indiana

Twin Caves (Lower Cave)

Mosquito Creek is typically much shallower, but the Indiana Department of Natural Resources and Civilian Conservation Corps built a dam here to facilitate flat bottom boats to navigate the stream. Launching off from the dock, guests are able to travel 500 feet into Upper Twin Cave to tour this unique stretch of cave filled  with karst windows. These sinkhole openings to the surface create openings in the cave ceiling much like the “cenotes” of Mexico. During the winter season, caving groups regularly hosts tours of this section of the cave for NSS members. Walking, climbing, and swimming are all required to make it through the first half of the journey. On the opposite side of Upper Cave is the opening to Lower Cave. The stream here is much shallower thanks to the dam, allowing visitors to explore a little further into the cave, but not all the way. The passage connecting Twin Caves to Bronson Cave is considered extremely dangerous and closed to everyone. After rock skipping a dozen feet under the opening, one emerges inside of a large dome shaped cave room.


big cave room inside lower cave within Mitchell Karst plains nature preserve in spring mill state park Indiana

It was in a cave room such as this that IU ichthyologist, Dr. Carl Eigenmann made his world famous discovery of blind cave fish. Having traveled all over the world in search of these elusive creatures, it was while studying in his own backyard of Indiana that he discovered the Hoosier Cavefish. The Shawnee Cave System is also home to the depigmented Northern Cave Crayfish and several other rare invertebrates. Leaving the Twin Caves area, I climb out of the sinkhole back towards the parking lot to our next stop along Trail 3. With Bronson Cave being only a short distance from here, I decide to backtrack a bit along Trail 3 before starting the bulk of the hike. This portion of the trail travels through the eastern edge of the Mitchell Karst Plains Nature Preserve. If you were to zoom out over the area and look at the rolling landscape, it would look like the surface of a golf ball. The dimpled indentations throughout the Mitchell Karst Plains visible everywhere along Trails 3 and 5 are all sinkholes. Within the park, the sinkholes number more than 100 per square mile and reach a known maximum of 1,023 in a square mile near the town of Mitchell.


Bronson Cave overlook inside Mitchell Karst plains nature preserve within spring mill state park

Bronson Cave

It’s roughly a 10 minute stroll just past Twin Caves heading west to reach the entrance of Bronson Cave. Its opening is located at the bottom of another massive sinkhole in a wooded valley. A staircase takes visitors down to an overlook above this major cave collapse to get a birdseye view of the area. Unlike the sinkhole at Twin Caves, the Bronson Cave sinkhole is filled with an enormous rock fall. Towering slabs of limestone litter over the stream where a continuous passageway of Shawnee Cave once existed. Feeling adventurous, I walked down the hillside into the sinkhole and followed the stream into the dark cave opening to find a large water filled rotunda. Though the two separate sections go by different names, Bronson Cave is simply the southern opening of Donaldson Cave. As a whole, they are known as Shawnee Cave. 


overlook of Bronson Cave in Mitchell Karst plains nature preserve within spring mill state park Indiana

This is the second section of cave open to NSS tours and features what some consider one of the largest “big rooms” in Indiana. A highlight of this tour are two natural water slides created by cascading waterfalls. Though archeological studies have not been conducted within the Shawnee Cave System, Lawrence County as a whole is filled with numerous early prehistoric sites. Mounds, cave dwellings, and village sites have all been discovered near the towns of Bedford and Mitchell, as well as the banks of the White River nearby. Just north of here near the abandoned community of Palestine, residents discovered a circular stone wall surrounding a prehistoric mound containing a stacked burial chamber dating to 1230 C.E. Among the many human remains and cultural artifacts recovered, was the skeletal remains of a man thought to be nearly 7 feet tall. It is one of hundreds of abnormally large “giant” skeletal remains found all around the world.


inside of Bronson Cave in Mitchell Karst plains nature preserve within spring mill state park Indiana

Donaldson Woods Nature Preserve

A few miles away near the town of Huron is the Connelly Cave and Mound Site. Here existed a cluster of seven mounds measuring two to four feet high, arranged in a winding pattern similar to other effigy mounds found throughout the Midwest. Those are just a few examples of the complex prehistoric civilization that once existed in the region known as the Oliver Phase of Central and Southern Indiana and might have at one point come into contact with the Shawnee Cave System. As I exit the sinkhole of Bronson Cave, I make my way back to the Twin Caves parking lot heading east towards the Donaldson Woods Nature Preserve. To some folks it might be easy to dismiss this as just “any ole’ forest” until you notice that some of these trees are unusually big. Donaldson Woods contains the third largest tract of old growth “virgin” forest outside of Pioneer Mother Memorial Forest and Hoosier National Forest. Some of these tall specimen quality trees are anywhere from 200 to 300 years old. 


old growth forest in Donaldson Woods Nature preserve within spring mill state park Indiana

Aside from the caves, this was George Donaldsons pride and joy. From the moment he purchased the property, he would not allow anyone to hunt, cut wood, or pick herbs or plants on this property. Over top of the dense understory of pawpaw and sugar maple exists a large number of oaks which are known to reach a staggering 120 feet tall. Out of all the tallest trees in the state, most of them are ancient oaks.  I stopped dead in my tracks as soon as I spotted the first of these giants decomposing just off-trail. Walking over to this fallen snag, I was dumbfounded by its size. Laying on its side, the tree was a hair taller than me at six feet wide. Mother Nature was busy at work turning this once living giant into new hummus rich soil for the hundreds of plants nearby. A miniature ecosystem of its own, this dead tree is teeming with life as an array of termites, ants, beetles, millipedes, and fungi begin colonizing and feeding on its remains.


old growth forest of Donaldson Woods Nature preserve within spring mill state park Indiana

Snags like this one also provide essential habitats for squirrels, raccoons, bats, and wood ducks. Though not yet in bloom, I was able to find small colonies of leafed out Trillium and Yellow Trout Lilies. Intermingled with them were the painted leaves of Virginia Waterleaf with their stalks getting ready to unfurl any day now. In a few far off corners I could see the foliage of some solitary Dutchman Breeches, but I’m not sure if its in the process of blooming or if the pearly white flowers have already come and gone. Of Indianas original 20 million acres of forest, fewer than 2,000 acres of old growth forest remain intact. Donaldson Woods is a monument to the once massive eastern deciduous forest that stretched from the Atlantic coast to the prairies of the Midwest. In 1972, Donaldson Woods was honored with the designation of a National Natural Landmark.

flowering periwinkle vinca within Donaldson Woods Nature preserve of spring mill state park Indiana

Donaldson Cave Nature Preserve

The perimeter of Donaldson Woods ends near the trail crossing down the road from Spring Mill Inn. As one of Indianas State Parks most revered and wondrous lodges, it was a project that almost never happened. Designed by the Indiana Conservation Department, the project began with the clearing of the site by the Civilian Conservation Corps in 1936. During the initial phase of construction, a large cave was discovered underneath the foundation of Spring Mill Inn. Before the widespread use of electric air conditioning, the idea to pump cool air from the cave to act as a natural air conditioning for the building was considered. Built from local limestone sourced from quarries in nearby Stonington, the Inns structure was meant to honor and evoke the states pioneer history. Originally designed to be much larger, financial constraints forced engineers to cancel the construction of a planned east wing. The state of Indiana was finally able to finance the rest of the project by selling huge quantities of sand to the City of Chicago, Illinois to use as fill material during construction for the Worlds Fair.


mill creek flowing through Donaldson Cave nature preserve in spring mill state park Indiana

Just past Spring Mill Inn, Trail 3 enters the boundary of Donaldson Cave Nature Preserve. Atop a hill to the right of the main trail is a short spur that leads to the Inn and what’s left of two overnight cabins dating back to the construction of the park. From the outside looking in, these cabins project what every kid imagines summer camp would look like. While not open to the public, one of them is in bad enough shape that the door is missing and you can walk inside to see the dilapidated roof and floors completely caved in. The area leading up to the cabin is completely engulfed with pastel blooms of periwinkle vinca. This wide spreading European and Asian native was more than likely used as a way to combat soil erosion before its invasive and destructive nature was truly known. Currently, the vision of Nature Preserves holds annual invasive species cleanups here to try and remove the colorful vines from this area.


cascading waterfall along mill creek in Donaldson Woods Nature preserve area of spring mill state park Indiana

It’s a short stroll from here to Donaldson Cave. To reach the cave, turn RIGHT on the spur trail heading west to the Donaldson Cave Overlook. This sneak peak into the Mill Creek Valley is only visible during the leafless months of the year. Getting down to the creek requires  walking down seven flights of stairs, which are easy enough going down, but strenuous on the way back up. This idilic valley is thought to look much the same as when George Donaldson first laid eyes on it. Legend has it that after purchasing the property, Donaldson would stand guard with a rifle over the opening of the cave, to fend off trespassers. Caves were some of the earliest sources of gun powder in the form of saltpeter and an easy source of income at the expense of the caves themselves.


entrance to Donaldson Cave in Donaldson Cave nature preserve area of spring mill state park Indiana

During one of Donaldsons long journeys, he received word that his six-room cottage in “Beautiful Shawnee” was looted and subsequently burnt to the ground. He would never return to visit his estate in Indiana. This upcoming summer (2022), archeologists from Indiana University will be excavating the site where the cottage was located in hopes of finding artifacts from Donaldsons home. In the intervening years between George Donaldson leaving the property and the state acquiring it, settlers from the nearby Village of Spring Mill made use of the cave. Due to Mill Creeks consistent temperature year round, it has the unusual affect of never freezing during winter. This led a local named Isaac Fife to build a flume extending all the way into the mouth of Donaldson Cave to power a gristmill and later a wood mill that was operated here on the banks of Mill Creek. Villagers also utilized the caves cool environment as a place to butcher meat and cool perishable food. 



Donaldson Cave underground passageways in spring mill state park Indiana

In 1972, the entire gorge leading up to the entrance of Donaldson Cave was designated as a nature preserve. Today it serves mostly as a splash park for kids playing in the creek at the mouth of the cave. This is one of the largest natural cave openings in the state. Walking into its vast entrance, you can hear the roaring cascade of that final waterfall slide cavers must trespass on the way out. Stacked stone blocks leading up one of the caves shorter passageways leads visitors on a miniature  journey to a secret cave entrance in the hill above Mill Creek. Self Guided caving tours are common here but permits must be obtained from the park office first. After enjoying some time spent along Mill Creek and Donaldson Cave, it’s a heck of a trip back up the roughly 80 steps to the ridge top. From Donaldson Cave, Trail 3 continues another 1.25 miles through the Mitchell Karst Plains Nature Preserve back to where we parked at Twin Caves. During winter this is mostly a peaceful and quiet hike. With so many budding trees and emerging wildflowers, I’’ll have to revisit Spring Mill later on in the season to get a better appreciation of its natural beauty.


gristmill in pioneer village within spring mill state park Indiana

Bonus: Hamer Cave & Pioneer Village

After my tour of Trail 3, I had just enough time before sunset to take a driving tour of the park and make a quick stop to see the Pioneer Village and Hamer Cave. The main road loops around the entire property, but becomes a one way lane beginning at Spring Mill Inn. Just past the peaceful Spring Mill Lake and Nature Center is the parking lot and trailhead for Trail 4 which runs through the heart of the village. In 1814, Samuel Jackson Jr. built the first dam and gristmill along Mill Creek. A few years later, the Bullitt Brothers purchased the property and built the present day dam, flume, and gristmill below Hamer Cave. The heyday of Spring Mill Village took place during Hugh Hamers ownership of the mill. He was initially brought in by the Bullitt Brothers to operate the mill and eventually bought the property from them in the 1830’s. The Hamers were close friends of George Donaldson and were some of the folks who alerted him of his home burning to the ground. 


19th century pioneer village inside of spring mill state park Indiana

All of the buildings you see in the village were reconstructed by the Civilian Conservation Corps in the 1930’s. Aside from the gristmills stone foundation, most of the wood used to rebuild the village was sourced from existing pioneer cabins found throughout Indiana. During the summer months, the park hosts regular reenactments of how pioneer life might have looked when the village was fully inhabited. The Friends of Spring Mill State Park organization has a historical database on its website filled with early photos dating back to when the village was inhabited, through its abandonment, and rehabilitation by the CCC.  Part of what made the Village of Spring Mill so successful was its location along one of the main stagecoach routes crossing the southern half of Indiana from the towns of Vincennes to Lawrenceburg (Hwy 50). At the turn of the century, as the railroad network began to extend west, a new rail line was built bypassing Spring Mill with a direct stop at nearby Mitchell. 


hamer cave and dam inside of Mitchell Karst plains nature preserve and spring mill state park Indiana

Following the small footpath along Mill Creek, I pass the gristmill and reach the top of the dam with an overlook of Hamer Cave. Just to put things into perspective, geologists believe that at some point in history Hamer Cave and Donaldson Cave were all connected to a much larger Shawnee Cave system. They surmise that cave collapses throughout thousands of years were responsible for creating this valley and the depression that would fill in to become Spring Mill Lake. This modern concrete version of the dam was built by the Lehigh Cement Company in 1902. A pump house in the center of the small lake diverts water from Hamer Cave to the cement plant to cool their kilns. Though they still operate the dam and pumphouse, the Lehigh Co. donated 300 acres of land surrounding the village to help create Spring Mill State Park in the 1920’s.

gristmill inside of spring mill state park Indiana

There is so much to see here and I could spend an entire day just roaming through each and every log cabin and write an entire article dedicated to it, but we will have to save that for another occasion. If you find yourself near Mitchell, Indiana make sure to make a stop here and check out the boat tour at Twin Caves and take a walk around the village, at the very least. Also check out the nearby Bluespring Caverns Cave Tours (which is one of my favorites) or take a nature walk through Cave River Valley Natural Area. Until next time, see y’all in the trails!


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