Emily Flores
Have you wondered what hides under the everyday streets we walk on? Turns out, there are lakes, ghost towns, caves, music halls, and even secret bunkers hidden below. These underground spaces mix wonder and weirdness, proving adventure doesn’t always mean climbing up—it can mean heading down.
Greenbrier Bunker, West Virginia
Hidden beneath a luxury resort in West Virginia sat one of the Cold War’s biggest secrets—the Greenbrier Bunker. Built in the late 1950s to shelter Congress, the underground complex had dorms for over a thousand people, plus heavy blast doors. It stayed hidden for decades before being revealed in 1992, and today, it’s a museum.
Seattle Underground, Washington
After the famous 1889 fire, the Seattle Underground was constructed with the streets raised above the original city. So, preserved arches and tunnels remain below modern blocks. Once serving as shops and passageways, the concealed spaces reveal Seattle’s early commercial struggles. Walking tours now showcase these layers of history and urban adaptation.
Bluegrass Underground, Tennessee
Located literally inside a cave, the Bluegrass Underground in Tennessee lies 333 feet beneath the surface. Known for its remarkable acoustics, it now hosts live performances ranging from bluegrass to other genres. Artists and fans value the sound and setting, where natural geology blends seamlessly with cultural expression in an unforgettable venue.
Mammoth Cave, Kentucky
Kentucky’s Mammoth Cave holds the record as the world’s longest cave system, with 426 miles already mapped and counting. Recognized as a U.S. National Park and also a UNESCO World Heritage Site, it offers guided tours featuring striking formations and fossils. In fact, for millennia, people have sought shelter and discovery within its depths.
Devil’s Den, Arkansas
Deep within the Ozark Mountains, Devil’s Den State Park lures explorers with dramatic sandstone crevices and winding trails. The most remarkable feature is the prehistoric underground spring. Hidden in a 120-foot-wide cave, it’s also a famous diving spot where nature lovers encounter striking geology and a timeless reminder of Arkansas’s natural wonders.
Louisville Mega Cavern, Kentucky
Once a massive limestone quarry, Louisville Mega Cavern now offers thrilling underground adventures. Spanning 17 miles of corridors, it features ziplines, bike trails, and tram tours. The cavern’s unique engineering and scale further create an unmatched setting, where history and geology converge beneath the bustling city of Louisville.
Lost Sea Cave, Tennessee
This is where the nation’s largest underground lake, second only globally, exists. Visitors explore the crystal waters of Lost Sea Cave in Tennessee by glass-bottom boats. The cavern carries Native American and Civil War connections, which add depth to its natural appeal. Its vast waters and limestone formations also mark it as a rare American wonder.
Fantastic Caverns, Missouri
Located in Springfield, Fantastic Caverns is America’s only ride-through cave. Discovered by John Knox and his hunting dog in 1862, its guided jeep tours reveal glittering stalactites and ancient formations. The cavern’s accessibility and historical significance make it a rare destination, offering geological education alongside an unforgettable underground experience for all ages.
Indiana Caverns, Indiana
Glittering crystals and dramatic rock formations define Indiana Caverns, recognized as Indiana’s largest cave system. Adventurers ride boats along its underground river for rare views, as fossil discoveries highlight their scientific value. Educational tours emphasize geology and paleontology, while protected status ensures this underground treasure remains preserved for generations.
Moaning Cavern, California
California’s Moaning Cavern, named after the haunting sounds echoing from its depths, features the largest single cave chamber in the state. Explorers can rappel down or take spiral stairs to marvel at stalagmites and stalactites formed over millennia. Over here, every corner tells a story of time, leaving visitors both humbled and fascinated.
The Florida Caverns State Park, Florida
The only state park in Florida where you can enjoy cave tours, Florida Caverns State Park, showcases limestone passages and stalagmites shaped by thousands of years of water. Above ground, visitors also enjoy camping and fishing. This rare underground environment contrasts strikingly with Florida’s famous beaches and creates an unexpected adventure.
The Forestiere Underground Gardens, California
Built by Sicilian immigrant Baldassare Forestiere, these hand-carved gardens in Fresno feature subterranean courtyards and fruit-bearing trees. Inspired by ancient Roman designs, Forestiere created a cool refuge from California’s heat. Today, the Underground Gardens highlight ingenuity and the artistry of blending architecture with living elements, drawing curious travelers worldwide.
The Brewery Tunnels, Minnesota
Beneath St. Paul lies a labyrinth of sandstone tunnels once used by breweries to store beer at cool temperatures. However, these Brewery Tunnels also hold stories of Prohibition and immigrant life. Exploring them reveals a fascinating chapter of Minnesota’s industrial past, where geology met necessity to fuel the city’s brewing heritage.
Homestead Crater, Utah
In Utah’s mineral dome, the Homestead Crater shelters warm waters that stay between 90 and 96°F year-round. Visitors can even swim or dive year-round in its mineral-rich waters. The enclosed hot spring supports unusual aquatic life and offers a rare chance to experience recreation within an underground geothermal environment.
Marvel Cave, Missouri
Marvel Cave in Missouri is famed for its vast chambers, including the Cathedral Room, and occasional underground waterfalls. Originally mined for lead and barite, it later opened to the public as a show cave. And since the late 1800s, it has drawn tourists with boat rides and dramatic geological formations.
Butte Underground City, Montana
The Butte Underground City celebrates Montana’s copper mining heritage through preserved tunnels once used by miners and as utility passages. Inside, artifacts and equipment document the area’s industrial era. Guided tours share stories of mining life and show how frontier towns adapted to subterranean spaces for survival and work.
New York City’s City Hall Subway Station, New York
New York City’s City Hall Subway Station stands as an ornate relic of early transit. Opened in 1904, its vaulted ceilings and stained glass marked the grandeur of early subway design. However, closed in 1945, it now survives as a hidden architectural gem, glimpsed only from passing trains or rare tours.
Valley of Fire Cave, Nevada
Found in Valley of Fire State Park, this sandstone cave features vibrant rock formations and ancient petroglyphs. The site highlights Native American presence in the region and provides a striking mix of culture and geology. Sightseers also combine park hikes with cave exploration for both scenic and archaeological discovery.
Ellinwood Underground, Kansas
Beneath Ellinwood, Kansas, a network of tunnels preserves the forgotten life of a frontier town. Once bustling with saloons and shops serving railroad workers, the underground passages still contain original tools and furniture. Tours even highlight the community’s hidden social and commercial activity from the Santa Fe Trail era.
Ruby Falls, Tennessee
Concealed deep within Lookout Mountain, Ruby Falls showcases the deepest and also tallest underground waterfall open to the public in the United States. Illuminated for dramatic effect, the 145-foot cascade creates a breathtaking spectacle. Combining natural wonder with human ingenuity, Ruby Falls remains one of Tennessee’s most enchanting and enduring attractions.