Hidden River Cave

The nonprofit American Cave Conservation Association (ACCA) operates Hidden River Cave and the American Cave Museum as part of our educational initiative to support the protection of caves, karstlands, and groundwater resources.

The entrance (to Horse Cave) seems like a noble gateway to the birthplace of springs and fountains and the dark treasuries of the mineral kingdom. This cave is in a village (of the same name) which it supplies with an abundance of cold water, and cold air that issues from its fern-clad lips. In hot weather crowds of people sit about it in the shade of the trees that guard it. This magnificent fan is capable of cooling everybody in the town at once.”

— John Muir’s visit in 1867
Thousand Mile Walk to the Gulf

Hidden River Cave Entrance (photo by: Matt McClintock)
“The entrance (to Horse Cave) seems like a noble gateway to the birthplace of springs and fountains and the dark treasuries of the mineral kingdom. This cave is in a village (of the same the same name) which it supplies with an abundance of cold water, and cold air that issues from its fern-clad lips. In hot weather crowds of people sit about it in the shade of the trees that guard it. This magnificent fan is capable of cooling everybody in the town at once.”

— John Muir’s visit in 1867
Thousand Mile Walk to the Gulf

Hidden River Cave: An Environmental Success Story

Hidden River Cave is located directly beneath the City of Horse Cave in south central Kentucky. Its main entrance is at 119 East Main Street in the center of town! Hidden River Cave and the American Cave Museum are operated by the American Cave Conservation Association (ACCA), a national nonprofit organization committed to the protection of caves, karstlands and groundwater.

The cave was once the source of drinking water and hydroelectricity for the City of Horse Cave and offered commercial tours from 1912 through 1943. Groundwater pollution from domestic and industrial sewage, combined with the impact of low visitation during World War II and a lawsuit by the L&N Railroad led to the cave’s closing in 1943. For 50 years Hidden River Cave had been all but forgotten except during hot summer months when noxious fumes spewed from its enormous entrance.

In 1987 the American Cave Conservation Association relocated their national headquarters from Richmond, Virginia to Horse Cave at the invitation of William T. (Bill) Austin. Bill had approached two other caving organizations about creating an educational center at Horse Cave without success. As fortune would have it, ACCA was looking for a new home and jumped at the opportunity.

A planning grant from the Economic Development Administration provided funding for a feasibility study and Horse Cave seemed like the perfect place for a national cave and karst center. The site was in an internationally significant cave area near Mammoth Cave National Park, the educational and environmental needs were obvious: a polluted cave right in the middle of town, and the location was in a major tourism travel corridor. At this same time a new regional sewage treatment system was also being developed by the Caveland Sanitation Authority and hopes were high that this would correct the groundwater problems in the cave. In 1989, this system went online.

With sewage no longer draining into the cave, a remarkable recovery began to occur. ACCA continued to raise funds for exhibits and to operate the Karst Center. In 1992, the first phase of the center opened to the public as the American Cave Museum. Since that time, we have raised approximately 7.5 million dollars for land acquisition, construction of the museum, additional exhibits, developing the tour into Hidden River Cave and to fund our ongoing educational and conservation programs.

Today, thousands of visitors and school children tour Hidden River Cave and the American Cave Museum. The museum and the cave, which has been called “the greatest cave restoration success story in the United States” is now open year-round to visitors.


An Early Source of Water and Electricity

The Village of Horse Cave was founded around 1850 on land surrounding the scenic entrance to Horse Cave. Before the modern era, native Americans and later, white settlers, made their homes around this good source of water.

As early as 1879, attempts were made to set up public waterworks in the cave. Not only did the cave stream provide drinking water, it later provided the necessary force to boost water into towering supply tanks that held water for fighting fires.

In 1888, Dr. George A. Thomas moved to Horse Cave to establish a dental practice. He purchased a house by the cave entrance and a year later purchased the cave for $375.00. He envisioned the cave as a source of both water and electrical power. Water from a spring in the north wall of the cave entrance was caught in a wooden tub and hauled up to a brick springhouse by a clever bucket trolley. Later, the south branch of the cave stream itself became the source of water for the town and the power to lift it to a standpipe located on the lip of the cave entrance.

In 1890, an ingenious vertical shaft turbine was erected below the confluence of the two cave streams to power a piston pump located near stream level and a booster pump located halfway to the surface. A large, grooved wheel with an endless cable powered the top pump. The addition of an electrical generator in 1892, provided electricity to the Thomas home, dental office, and two other buildings in town. This gave Horse Cave the distinction of being the first town in Kentucky to have incandescent lights. (Louisville, Kentucky was illuminated by electric arc lights earlier).

After Dr. G.A. Thomas’ death in 1905, his son, Dr. H.B. Thomas, also a dentist, bought the property and moved into the adjacent big house. He continued to operate the waterworks and installed a large three-cylinder pump on the ledge above the stream in order to increase the capacity of the system and simplify operations. This system remained in use until the early 1940s.

Historic hydroelectric system and water pumps at Hidden River Cave
Historic hydroelectric system and water pumps at Hidden River Cave. Photo courtesy of William T. Austin Family
1930s photo of Hidden River Cave tour group
A tour group visits Hidden River Cave circa 1930. Photo courtesy of William T. Austin Family

The Show Cave Era

In 1916, a half mile-long section of Horse Cave was opened to the public for tours. As part of a promotion Dr. H.B. Thomas ran a local contest to rename the cave, and the name “Hidden River Cave” was chosen for tourist use. Hidden River boasted elegant galleries and offered scenic tours along the river’s winding course through the cave. One of the tour’s most distinctive features, “Sunset Dome,” is a room at the end of the tour that is approximately 250 feet in diameter and 100 feet tall. The cave which has yet to be fully explored, was home to a number or rare cave creatures, including a large population of blind cavefish and blind cave crayfish.

The Destruction of the Cave

Since the time the Horse Cave area was first settled local residents dumped their trash and injected sewage into underlying cave passages, shallow wells, and nearby sinkholes, never realizing that they were contaminating Hidden River Cave and their own water supplies. By the mid-1930s, the town’s water supply was hopelessly polluted, and in 1943 noxious odors emitted by the cave’s pollution caused the closure of the tours. In addition to domestic sewage, wastes from local industries caused serious pollution and depletion of the stream’s oxygen. In the 1950s, vile odors permeated the entire business district of Horse Cave during the summer months, and the cave life completely died out.

In 1963, the community constructed a domestic sewage treatment plant. Unfortunately, the wastewater from this plant was dumped into dry wells which funneled into Hidden River Cave. Over the next two decades, the cave’s pollution problem grew even worse. In 1975, thousands of gallons of gasoline were lost into the cave system from a leaking tank. The gasoline fumes could be smelled in many local basements.

Hidden River Cave Entrance-1970s
Looking out of the Hidden River entrance in the 1970s with mud covering the stairway and debris strewn about.
Volunteers at the first Hidden River Cave Cleanup
Volunteers at the first cleanup project in the Hidden River Cave sinkhole around 1987.

The Cave’s Recovery

For several decades the grossly contaminated Hidden River Cave lay neglected and shunned by humans. The cave streams were void of life, except for strings of sewage bacteria and writhing bloodworms that thrived in the nearly oxygen-free underground waters. Gone were the once-plentiful blind cavefish that, like most animals adapted to living in cave streams, require highly stable conditions. The entrance to the cave was nearly invisible to passersby, surrounded by buildings, thick vegetation, and a high fence. It was easy to ignore the cave, except during each summer when the horrible stench of raw sewage belched from its mouth and reminded everyone of its presence.

In December 1989, sewage stopped flowing into the cave, thanks to a new state-of-the-art sewage treatment system built for the communities of Horse Cave and Cave City. Treated sewage from these two plants now enters a carefully studied and designed conveyance line which transports the wastewaters to an appropriate disposal site which will not damage groundwater supplies. This was part of a state and federally funded project costing many millions of dollars to restore the groundwater quality of the whole region. The terrible odors soon were gone and the cave stream was on its way to naturally restoring itself.

By the summer of 1991, the underground river had taken on enough oxygen to once again support indigenous life. Numerous crayfish had migrated to previously polluted sections to feast on dying sewage organisms. As the process of recovery continued and conditions stabilized, more native cave animals began to colonize the passageways.

ACCA Board and Staff During Strategic Planning Meeting around 1998
American Cave Conservation Association Board of Directors and Staff attend a strategic planning meeting in 1998

The Opening of the American Cave & Karst Center

In 1992, cleanup efforts Hidden River Cave’s large sinkhole entrance began to restore the lush setting described by John Muir after his 1867 visit. Exploration and mapping of the cave also resumed under the leadership of the ACCA after a 50-year hiatus. The full extent of the passageways is still unknown. In addition, plans to reopen the cave were considered. The first stage was accomplished in 1992 by improving the steps and walkway to the underground river.

Also, in 1992, the American Cave and Karst Center was established in historic buildings at the mouth of Hidden River Cave, once again calling attention to this remarkable natural feature: remarkable for its unique setting, it’s inherent beauty, its quintessential geology, and the successful rejuvenation of its underground river system.

A New Century Dawns

In 2013, Dr. Julian J. Lewis began a biological inventory of Hidden River Cave. The study found that Hidden River Cave’s once polluted passages were now home to twenty-one types of cave species, making the cave a global hot spot of subterranean biodiversity. In two decades, Hidden River Cave had transformed from one of the most polluted to one of the most biologically diverse cave ecosystems in the world.

By 2015, groundwater studies conducted by researchers from Western Kentucky University and Canada’s McMasters University concluded that Hidden River Cave’s water quality had recovered to near drinking water standards.

Blind Crayfish, Hidden River Cave
Looking out the Hidden River Cave entrance from inside

Securing the Cave’s Protection

Although Hidden River Cave was an amazing success story, there were still a few complex obstacles to overcome to ensure its protection.

In the 1930s it became very clear that what goes on above ground can severely affect what happens below the ground. A local landowner had erected a gasoline station on a lot that was directly above part of Hidden River’s developed tourist trails inside the cave. He then began disposing of sewage from the station’s restrooms into a hole drilled into Hidden River Cave. To complicate matters, the landowner did not own the cave rights – these were owned by the L&N Railroad Company.

In order to protect his investment, Dr. H.B. Thomas filed a lawsuit against the landowner in 1939. The Railroad joined the lawsuit to protect their property rights. Despite his compelling case, Dr. Thomas lost his suit. With no ability to protect the cave from the above ground activities, the Sunset Dome tour section of Hidden River Cave closed. By 1944, all of Hidden River Cave closed and the cave became known as one of the most polluted caves in America.With Hidden River Cave now on the road to recovery, ACCA began in earnest to search for a way to acquire the cave rights to permanently protect the cave. In 2012, ACCA secured funding from the Kentucky Heritage Land Conservation Fund to conduct an appraisal and purchase the cave rights.

With the grant approved, it took another year of complex negotiations with CSX Railroad, who had acquired the cave rights from L&N Railroad, and two local businesses that owned the surface rights.

In November 2005, the Mayor of Horse Cave joined state officials and the surface and subsurface cave property owners at the American Cave Museum to sign an easement to protect Hidden River Cave in perpetuity.

The Quest for Sunset Dome

With Hidden River Cave now an environmental success story and the protection that these new agreements put it place, work began to raise funds to construct the walkways and bridges into Sunset Dome. Funding came from the James Graham Brown Foundation, the Appalachian Regional Commission, the Dart Foundation and an anonymous gift from Friends of Bill Austin.

The first construction challenge was bridging the 50-foot-deep canyon that separated the end of the existing tour from Thomas Hall, the trunk passage leading to Sunset Dome. It was decided to build a 100-foot-long suspension bridge across the canyon. This would become the longest suspension bridge inside a cave in the entire world.

In November 2018 construction of the bridge was completed and opened to the public. Beyond the bridge, the construction slowly progressed towards Sunset Dome. Despite delays due to flooding and engineering issues, by the Fall of 2019, the new Hidden River Cave tour was about three quarters completed. It became clear that additional funds would be needed to finish the tour to Sunset Dome. An anonymous gift allowed ACCA to meet their bid estimates for the construction. After another delay due to flooding, concrete was poured for the remaining walkway section to open the Sunset Dome tour in February 2020. After being closed for 76 years, Sunset Dome was now again accessible!

Hidden River Cave's Sunset Dome

Thank You for Reading!

The story of Hidden River Cave is not only an environmental success story, it is a testament to the perseverance and faith of everyone involved from a small nonprofit that took the leap of faith to move their operations to Horse Cave, Kentucky with no tangible promise of success, to the many volunteers, community leaders and gracious foundations and agencies who supported and believed in this effort.

Eurycea lucifuga-photo by Lisa Powers
Eurycea lucifuga
photo by Lisa Powers

Hidden River Cave & The American Cave Museum are operated by the American Cave Conservation Association,

A National 501 (c) 3 Nonprofit Organization.

Pin It on Pinterest

Share This