1. The Bunker at the Greenbrier – White Sulphur Springs, West Virginia
This one is for the history lovers and fans of Cold War-era intrigue. Hidden beneath the luxurious Greenbrier Resort, the Bunker was once a top-secret fallout shelter for members of Congress during the Cold War. It wasn’t until 1992 that the bunker’s existence was publicly revealed, but now visitors can take tours to explore its fascinating history. Inside, you’ll find an entire underground facility, complete with dormitories, communication rooms, and emergency supplies—all preserved to look like they were ready for use at any time.
The Greenbrier Bunker gives a glimpse into the tense period of history when America feared nuclear attack and needed secret facilities for government officials. The tour includes a look at the shelter’s purpose, how it was built, and what life might have been like for those who would have used it in the event of an emergency. Visiting this underground site is both eye-opening and eerie, especially when you imagine how close we once were to using such a place. It’s a must-see for anyone interested in Cold War history, secret government operations, or unique underground experiences.
2. The Seattle Underground – Seattle, Washington
Seattle’s underground isn’t just some random network of tunnels—it’s a hidden layer of the city that history buffs will absolutely love. Back in the 1800s, the original streets of Seattle were built at a much lower level than they are today. After a massive fire in 1889, city leaders decided to rebuild at a higher elevation to prevent future floods. But instead of demolishing the old streets, they just built over them, leaving behind an eerie, forgotten city below the sidewalks. Today, you can take guided tours to explore this subterranean world, complete with old storefronts, cobblestone streets, and fascinating stories about Seattle’s rough-and-tumble pioneer days.
The tours are part history lesson, part adventure. Guides will spill the tea about everything from opium dens to secret passageways that were once used for less-than-legal activities. It’s also a perfect place to experience something truly unique—you’ll feel like a time traveler walking through what used to be bustling streets. Plus, it’s a little creepy, but in the best possible way. If you’re into ghost stories, you’ll love hearing about the supposedly haunted spots while standing right in them.
3. The SubTropolis – Kansas City, Missouri
If you’ve ever wanted to visit a literal underground city, SubTropolis is for you. Carved out of an old limestone mine, this 55-million-square-foot complex is now home to businesses, storage facilities, and even a few quirky events. The climate-controlled environment makes it a perfect spot for everything from housing valuable documents to growing mushrooms (yes, that’s a real thing that happens here). It might not have the historic charm of some other spots on this list, but it more than makes up for it in sheer coolness.
Visitors can take limited tours of the facility and get a glimpse of how this unique underground world operates. It’s mind-blowing to think that something so massive exists entirely out of sight. The juxtaposition of modern technology with the raw rock walls of the mine is something you just have to see to believe. Bonus: It’s one of the most energy-efficient complexes in the country since the underground temperature barely fluctuates.
4. Ruby Falls – Chattanooga, Tennessee
Ruby Falls isn’t your average tourist attraction—it’s a 145-foot underground waterfall inside Lookout Mountain. Discovered in the 1920s by an explorer named Leo Lambert, this natural wonder is now one of the most visited spots in Tennessee. To get there, you’ll take an elevator 260 feet below the surface and walk through a cavern filled with fascinating rock formations before arriving at the breathtaking waterfall. The lights and sound effects they use to highlight the falls make it an even more magical experience.
It’s also a great spot for families and anyone who loves a mix of adventure and nature. The guides are full of knowledge about the cave’s geology and history, so you’ll leave feeling like a bit of an expert on stalactites and stalagmites. Plus, it’s the perfect spot for photos—your Instagram feed will thank you. If you’re feeling extra adventurous, you can combine your visit with other outdoor activities on Lookout Mountain, like hiking or rock climbing.
5. The Winchester Mystery House Basement – San Jose, California
This one is a little less nature and a little more mystery. While the Winchester Mystery House is famous for its winding staircases, secret doors, and nonsensical architecture, the basement is a hidden gem that most visitors don’t even realize they can see. Sarah Winchester, the eccentric heiress who built the house, believed she was haunted by spirits and built the house to confuse them. The basement served as the hub for all the work done on the house, with boilers, coal chutes, and other equipment that kept the place running.
It’s dark, it’s damp, and it’s got an energy that makes you feel like you’ve stepped into a horror movie. Guides will tell you about the creepy occurrences reported by staff and visitors, from unexplained footsteps to doors slamming shut on their own. Even if you don’t believe in ghosts, the basement is a fascinating peek into the inner workings of one of America’s most bizarre architectural wonders.
6. Carlsbad Caverns – Carlsbad, New Mexico
When it comes to underground attractions, Carlsbad Caverns is in a league of its own. This massive network of caves features over 119 known caverns, some of which are open to the public. The star of the show is the Big Room, a huge underground chamber filled with jaw-dropping stalactites, stalagmites, and other formations that look straight out of a sci-fi movie. The National Park Service offers guided tours, or you can explore some of the more accessible areas at your own pace.
What makes Carlsbad Caverns extra special is its unique ecosystem. You’ll see bats flying out of the cave at sunset and hear about the tiny organisms that survive in the dark, damp conditions. If you’re lucky, you might even catch a ranger giving a talk about the cave’s history and how it formed over millions of years. It’s a must-visit for nature lovers, geology geeks, and anyone who wants to feel humbled by the sheer power of nature.
7. The Moffat Tunnel – Colorado
The Moffat Tunnel is one of the most important engineering feats in Colorado’s history. This 6.2-mile long tunnel, which runs through the Rocky Mountains, connects the cities of Denver and Boulder via the railroads. It was built in the 1920s to help streamline the transportation of goods and people through one of the most rugged terrains in the country. While not a typical tourist spot, it’s an intriguing and important piece of American infrastructure history.
While public access to the tunnel itself is limited, you can visit the surrounding areas, including the Moffat Tunnel Visitor Center, which gives you a deep dive into the history of the tunnel and the construction process. You can even view the tunnel’s portals from nearby lookout points. The sheer size of the tunnel and the fact that it goes under a mountain range that was once considered impassable will leave you in awe of early 20th-century engineering. Plus, the stories of the workers who risked their lives to build it add another layer of fascination to this underground marvel.
8. The Whispering Gallery at Grand Central Terminal – New York City, New York
Hidden right in plain sight, Grand Central Terminal in New York is home to one of the most peculiar underground features: the Whispering Gallery. Located near the Oyster Bar & Restaurant, this architectural quirk is not something you’ll see on your typical tourist guide but is worth seeking out. Due to the unique acoustics of the space, whispers can travel across the room with remarkable clarity, allowing someone standing on one side of the arch to hear someone’s voice clear as day from the other side.
The gallery’s acoustics are no accident; they’re a part of the terminal’s original design by architect Rafael Guastavino. It’s a fun little secret that can add a touch of whimsy to your visit. It’s also a cool spot for photos and for testing out the gallery’s acoustic quirks. Whether you’re just passing through or making a special stop, don’t miss the chance to experience this quirky feature of one of New York City’s most iconic landmarks.
9. The Luray Caverns – Luray, Virginia
The Luray Caverns in Virginia are another stunning natural wonder, and they are among the most famous cave systems in the United States. Formed over millions of years, the caverns are filled with breathtaking rock formations, including stalactites, stalagmites, and the world’s largest musical instrument—an underground pipe organ. The beauty of the Luray Caverns has made it a favorite for tourists, and the tour takes you through the cavern system while explaining the geology behind the rock formations and the history of the caverns’ discovery.
The caverns are well-lit, making them easy to explore, and the acoustics inside make it an otherworldly experience. The fact that they have a functioning musical organ inside the caverns makes it even more unique, as it plays hauntingly beautiful music in the natural acoustics of the cave. If you’re a fan of natural wonders and geology, Luray Caverns should be on your bucket list.
10. The Tunnel of Love – Chicago, Illinois
Located under the Chicago Botanical Garden, the Tunnel of Love is an enchanting underground feature you won’t find on many typical tourist itineraries. This isn’t a “secret” tunnel per se, but it’s definitely one of the hidden gems in the Windy City. This pathway runs beneath the Rose Garden, creating a serene, romantic experience where visitors can walk through a tunnel of lush greenery and vibrant blooms. It’s often described as one of the most beautiful hidden spots in the garden.
The tunnel itself is actually a network of pathways that lead visitors into the heart of the garden. As you wander through the foliage, you’ll find yourself enveloped in quiet, shaded surroundings with a sense of peacefulness that feels worlds away from the hustle and bustle of Chicago. Whether you’re there for a peaceful stroll or looking for a quiet moment, the Tunnel of Love is a romantic and calming underground attraction that’s perfect for couples or anyone who appreciates nature’s beauty.
11. The Cleveland Arcade – Cleveland, Ohio
While not exactly “underground,” the Cleveland Arcade is a historic gem that often gets overshadowed by larger attractions in the area. Opened in 1890, this grand shopping arcade was one of the first indoor shopping malls in the United States. Located beneath a gorgeous glass and iron skylight, the Arcade feels like stepping back in time, with its marble floors, high ceilings, and ornate design.
The Cleveland Arcade has a fascinating story, as it was designed to be a bustling hub of commerce and social activity. Today, it’s still operational and houses boutique shops, restaurants, and offices. But what makes it special is that it has a “lower” level, where you can enjoy the beauty of the space without the crowds. It’s a fantastic spot for history buffs, architecture enthusiasts, or anyone wanting to experience Cleveland’s unique history in a hidden corner of the city.
12. The Salt Mines of Cleveland – Cleveland, Ohio
The Cleveland Salt Mines are an underground treasure that most people don’t even know exist. Beneath Lake Erie, salt has been mined in Cleveland since the 1800s, and the operation is still running today, though not in the way you might expect. These salt mines are now open to the public for tours, where you’ll get to see how this once vital resource was extracted and learn about its long history in the region.
The tour takes you about 1,500 feet underground, where you’ll explore the vast chambers carved out of salt deposits. The environment is incredibly unique—cool and dry, perfect for preserving the salt, and it’s a bit like walking through a hidden underground world. Along the way, you’ll learn about the mining process, the geology of the area, and the fascinating history of the region’s salt trade. If you’ve never experienced a salt mine before, it’s a sensory journey, from the scent of the air to the visual oddities of the environment.
