Caves aren’t just home to bats and ancient relics; they also hide 10 cool things that will surprise even the most seasoned spelunker. From adrenaline‑pumping sports to secret sanctuaries, these subterranean surprises prove that the world beneath our feet is far more eclectic than anyone expected.
10 cool things You’ll Find Below
10 Mountain Biking
Mega Cavern Bike Park in Louisville, Kentucky, boasts the world’s first underground mountain‑biking trail system and claims the title of the largest indoor bike park ever constructed. The cavern’s towering 30‑meter (90‑foot) ceilings allow riders of every skill level to carve through winding paths, tackle jumps, and experience the sensation of descending a mountain without ever leaving the earth’s surface. Co‑owner Jim Lowry likens the experience to “riding or skiing down a mountain,” explaining that riders don’t just speed straight downhill; they weave back and forth over bumps and smooth stretches, alternating between bursts of speed and slower, technical sections.
Designed by ESPN X‑Games veteran Joe Prisel, the park follows a modular design that lets the team reconfigure trails throughout the year, constantly offering fresh challenges. The cavern maintains a steady 16 °C (60 °F) temperature, eliminating weather‑related hazards that plague outdoor biking. A riding school is also slated to help newcomers master the craft.
The 92‑acre underground complex also houses a business park and a range of attractions, such as the “Lights Under Louisville” drive‑through display featuring over two million Christmas lights. The cavern stretches beneath the Louisville Zoo and several commercial structures, yet the texture of the limestone walls and the varied earth feel surprisingly open, as if you’re on a mountaintop rather than underground.
During the Cuban Missile Crisis, the cavern’s massive limestone roof was deemed sturdy enough to serve as a fallout shelter capable of protecting up to 50,000 people. Excavated in the 1930s, the man‑made cavern was originally a limestone quarry for more than four decades. After changing hands in 1989, it transitioned to a recycling hub and later accommodated 11 acres of office space, evolving into a sprawling hidden metropolis within the limestone cliffs.
9 A Nightclub
Deep within Hotel Las Cuevas in Trinidad, Cuba, Disco Ayala transforms a natural cavern into a pulsating rave haven. The venue features three bars and five dance floors, blasting disco‑salsa beats from a DJ booth while vibrant lights bounce off stalactites. An opening in the roof releases some of the heat generated by the party, but it also serves a crucial structural purpose: it prevents sound waves from building up enough pressure to cause a cave‑in. The cavern can host up to 5,000 revelers, and live performances include acrobatics, glass‑eating, fire‑walking, and even snakes.
Local legend claims the cave once belonged to infamous Cuban serial killer Carlos “Coco” Ayala, who allegedly kidnapped and murdered children there during the 19th‑century Cuban War of Independence. Parents still warn misbehaving children, saying, “Be good or Carlos Ayala will come looking!” Historical records confirm that Ayala committed several murders inside the cavern in the late 1800s, though the exact details are murky. Despite the grim folklore, the club’s owners retained the Ayala name, repurposing the space solely for entertainment rather than as a memorial to the murderer.
8 A Church
Carved into a chalky cliff in the Voronezh region’s Kostomarovo village, the Spassky Cave Church forms the larger of two sanctuaries belonging to the ancient Svyato‑Spassky Convent. Despite its subterranean setting, the church can seat roughly 2,000 worshippers and even includes a “Cave of Repentance” where sinners can confess. The surrounding landscape mirrors biblical geography, featuring a Calvary, a Gethsemane garden, a Golgotha hill, and a Mount Tabor.
Before Christianity took root in Russia, hermits and monks sought refuge in isolated cave cells to escape persecution. By the 12th century, the first monastery was erected, offering protection against enemy sieges. Monks lived in cramped rock‑cut cells, isolated from the outside world except for a tiny window. During the Soviet era, the convent was shuttered, its monks executed, and the caves later served as shelters for soldiers in World War II. The church briefly reopened in 1943, only to be closed again in the early 1960s under Khrushchev, who ordered the caves flooded and the exterior structures burned.
Following the Soviet Union’s collapse, the complex was rebuilt in 1993. Today, pilgrims continue to travel to the cavernous sanctuary, preserving a centuries‑old tradition of worship beneath the earth.
7 A Whole New Ecosystem
China’s Er Wang Dong cave, nestled in the Chongqing province, is so expansive and secluded that it nurtures an entirely self‑contained ecosystem, complete with its own weather patterns. Researchers only managed to explore its depths in 2012 because reaching the entrance demanded a 250‑meter (820‑foot) vertical descent using specialized gear. Once inside, the team discovered a series of natural openings that linked the interior to the surface, as well as a stunning 13‑acre chamber where clouds perpetually hover—a phenomenon known as Cloud Ladder Hall.
These clouds drift in but cannot escape, creating a surreal mist‑filled ceiling. Though the cave once yielded nitrate deposits, its inner chambers now boast lush vegetation, including full‑sized trees. However, explorers must remain vigilant, as swift underground rivers can surge, sweeping adventurers over cascading waterfalls.
Explorer Robbie Shone notes the profound mystery still surrounding subterranean realms: “More people have been to the Moon than to some of these caves. Each expedition brings back images and footage that reveal completely new, never‑seen phenomena.”
6 Modern Cavemen And Cavewomen
In China’s Shaanxi province, roughly 30 million people still call caves home, inhabiting dwellings known as yaodong. The loess plateau’s porous soil makes it simple to carve out a single‑room cave residence directly into the mountainside. These modest homes often replace a front door with a sheet of rice paper or a quilt, though wealthier occupants can expand their space, add electricity, running water, and even a small yard. The natural insulation keeps interiors cool in summer and warm in winter, providing an energy‑efficient lifestyle and freeing up surface land for agriculture.
Demand for these subterranean homes has risen, with many prospective buyers eager to rent or purchase. Yet residents rarely leave; many have spent their entire lives underground. Ren Shouhua, a forty‑something local, explains, “It’s cool in the summer and warm in the winter. It’s quiet and safe. When I get old, I’d like to go back to my roots.”
Historically, the caves have also been sites of tragedy. The 1556 Shaanxi earthquake—recorded as the deadliest in history—claimed 830,000 lives, many of whom perished when their yaodongs collapsed. Nevertheless, caves have offered refuge during pivotal moments: Mao Zedong’s forces retreated to Shaanxi caves after the Long March, and during the Cultural Revolution, President Xi Jinping spent seven years living in a cave exile.
Not all cave dwellings are humble. The deluxe Cave House in Bisbee, Arizona, listed for over $1 million in 2012, demonstrates the high‑end market for subterranean real estate. Even eBay has seen cave homes sold, such as the 2003 purchase by Curt Sleeper in Festus, Missouri, though financing proved challenging and the property eventually went to auction.
5 Medical Treatment Centers
Two French women, convinced that modern electromagnetic radiation was harming their health, sought solace in a remote cave. One of them, Bernadette Touloumond, lamented being treated “like a crazy woman” and noted the loss of friends and family misunderstanding. Across the globe, numerous medical facilities have been established within caves, promising therapeutic benefits for a variety of ailments. The Gastein Healing Cave in Austria, for instance, hosts the world’s largest pain‑management center.
Salt caves—both natural and artificially constructed—have surged in popularity as halotherapy venues. These spaces line walls and ceilings with salt, sometimes using generators to disperse fine salt particles into the air. Visitors relax in chairs, breathing the mineral‑rich environment, which is claimed to alleviate respiratory issues like asthma and skin conditions such as eczema. However, physicians caution that halotherapy may exacerbate certain conditions, particularly severe asthma.
German physician Dr. Schutz pioneered the concept after observing accelerated wound healing near a Polish salt mine during World II. Today, salt‑cure galleries are common throughout Eastern Europe, though scientific research on their efficacy remains limited, especially in English‑language publications.
4 A Controversial Movie Set
Devetashka Cave, situated near the Bulgarian village of Devetaki, has a layered history: from a 1950s military oil‑tank warehouse to an ancient human habitation site. Presently, the cavern protects a thriving bat population, including several endangered species. In 2011, the cave entered the global spotlight when producers of The Expendables 2 staged a dramatic action sequence, having Sylvester Stallone crash‑land a plane inside the cavern to confront Jean‑Claude Van Damme’s hideout.
Environmental activists argued that the shoot decimated the bat colony, claiming a 75 % reduction. Zoologist Nikolay Simov of the Center for Bat Studies and Protection explained that props, vegetation removal, and the sheer number of crew members generated noise and disturbance, forcing bats out of hibernation prematurely. Simov also noted that local officials lacked legal authority to grant filming permits, as the cave’s regulations only permit scientific research and tourism.
Subsequent investigations by Bulgaria’s Ministry of Environment and Waters found that most bats were indeed hibernating at appropriate times and that the mortality rate was not as severe as initially reported.
3 Astronomical Knowledge & A Fertility Light Show
On Gran Canaria, one of Spain’s Canary Islands, a cave once serving as a Guanche temple reveals an astonishing grasp of astronomy. The interior aligns perfectly with equinoxes and solstices, suggesting sophisticated celestial knowledge among the island’s pre‑colonial inhabitants. Archaeologist Julio Cuenca describes the cave as “a projector of images from a vanished culture.”
The temple creates a seasonal light display that mirrors fertility myths. From March to September, sunlight filters onto the walls, casting phallic projections over engravings of female pubic symbols. As autumn approaches, these images morph into a pregnant figure and finally a seed, illustrating a cyclical narrative of life and reproduction.
2 An Amusement Park
While technically not a cave, the Wieliczka Salt Mine near Kraków, Poland, has transcended its mining origins to become a subterranean amusement park. The 300‑kilometer (186‑mile) complex spans nine underground levels, featuring chapels, elaborate sculptures, and a massive cathedral—all carved from salt by generations of miners since the 13th century. The mine also boasts an underground lake and dazzling salt chandeliers.
Visitors can partake in extreme activities such as bungee jumping, hot‑air balloon rides, and even windsurfing across the lake—though a giant fan provides the necessary breeze. An on‑site brass band adds a festive soundtrack, while a dedicated spa offers halotherapy for those with respiratory ailments. In 1978, UNESCO recognized the site as a World Heritage treasure.
1 Hidden Treasure
In March 2015, 21‑year‑old Hen Zakai of the Israeli Caving Club stumbled upon an ancient cache while exploring a concealed stalactite cave in northern Israel with his father and a friend. Navigating a narrow passage, Zakai’s torch caught the glint of two silver coins minted during Alexander the Great’s era, each bearing the conqueror on one side and Zeus on the other. Nearby, a cloth pouch contained remarkably preserved silver jewelry—earrings, bracelets, and rings.
Dr. Eitan Klein of the Antiquities Authority theorized that the treasure was hidden by locals fleeing the turmoil following Alexander’s death, during the Wars of the Diadochi. The cache appears never to have been retrieved, leaving the artifacts untouched for over two millennia. Further exploration revealed ancient pottery fused to stalagmites, dating from the Hellenistic period (about 2,300 years ago) back to the Chalcolithic era (roughly 6,000 years ago).
Authorities have kept the cave’s exact location confidential to prevent looters from exploiting the site, ensuring that the hidden trove remains protected for future archaeological study.