LIFE BELOW GROUND
Some of the coolest spots you’ve never heard of may lie right beneath your feet. From one-of-a-kind caves to commuter walkways to “underground cities” from the early 1900s, there are many places to find adventure below ground. Some of these are free to explore, while others collect an entrance fee of no more than $20, which includes a guided tour.
Related: Offbeat Attractions in All 50 States
NEW YORK CITY LOWLINE
New Yorkers and visitors have likely strolled along the High Line, a repurposed elevated rail track that runs through part of Manhattan’s West Side. But how about the Lowline? This project-in-progress would use solar technology to turn a historic trolley terminal on the Lower East Side into an underground park. Currently, visitors can stop by the Lowline Lab, a free exhibit that demonstrates how the Lowline would grow and sustain plants underground.
Related: 50 Free and Cheap Things to Do in New York City
Chicago can swing between oppressively hot and chillingly cold, but the city’s underground Pedway takes the pain out of the weather for pedestrians. About 5 miles of hallways connect buildings and train stations in a 40-plus-block area of the central business district. It’s free to walk through.
Atlanta boasts its own “city beneath the streets” in the Five Points neighborhood. Stretching over the equivalent of six city blocks, the area encompasses three underground levels filled with shopping, restaurants, and entertainment. There’s even a weekly underground food-truck convergence with more than 60 vendors.
The “Great Seattle Fire” destroyed 31 downtown blocks of walkways and basements in the mid-19th century. After the streets were elevated, the network of abandoned underground spaces became a historic attraction. Touring the area costs $20, but reviewers on Google give the tour -- especially the entertaining guides -- high marks.
A network of passages between buildings snakes underground in Portland, Oregon. Called the Shanghai Tunnels, they were used in the 19th century for illegal activities, including as a holding place for men forced into servitude aboard ships. The tunnels are now open to the public with a $13 guided tour ($8 for children under 12).
WABASHA STREET CAVES
These sandstone caves, carved out during the mid-1800s, are accessible from downtown St. Paul, Minnesota. Once upon a time they were the scene of mobster meet-ups and housed speakeasies, but these days the caves are the setting for tours and select nights of live, big-band music. The caves can be toured for $6.
With 32 miles of caves and underground passageways, this national natural landmark in McMinnville, Tennessee, is one of the longest caves in America. Besides being a site for tours and exploration, the caves are also the venue for Bluegrass Underground, a musical performance broadcast regularly on PBS. The cheapest tour option is a family ticket for $65, which covers two adults and two children (ages 6 to 12).
BUFFALO BAYOU CISTERN
A drinking-water reservoir built in 1926 for the city of Houston, this underground marvel has just been repurposed as a public space that will house temporary art installations. It's free to tour the space on Thursdays and $2 at other times. Children under 9 are not allowed, and advance reservations are required.
MAMMOTH CAVE NATIONAL PARK
This national park in central Kentucky is the longest known cave system in the world. To date, 400 miles of the caves have been explored. Prices vary depending on the tour but are as low as $5 for adults.
APE CAVE LAVA TUBE
Ape Cave Lava Tube, located on the south side of Mount St. Helens in Washington, is the longest continuous lava tube in the continental United States. It’s also a popular hiking destination. The cave is free to visit, but daily parking costs $5.
Downtown Port Angeles, Washington, had a problem with constant flooding and high tides in the early 1900s. The streets were raised in 1914, leaving a network of underground tunnels that visitors can explore. Tours cost $15 for adults, and less for seniors, students, and children.
Niagara Cave in Harmony, Minnesota, is a geological wonder. Along the route of the 1-mile tour, visitors pass an underground waterfall, view ancient fossils and passageways created by an underground stream, and stop at a chapel where scores of couples have married. Admission is $14 for adults and $8 for children ages 4 to 12.
OLD SACRAMENTO UNDERGROUND
The city of Sacramento, California, is yet another community lifted above floodwaters during the latter half of the 19th century, leaving behind underground spaces. Tour the historical remnants with a guide for $15 ($10 for children). Reservations are advised.
HAVRE BENEATH THE STREETS
Fire destroyed the business district of Havre, Montana, in 1904. While the town rebuilt, business owners moved underground, creating a city beneath the streets. Visitors can tour spaces once used as saloons, markets, and even a bordello. Adults pay $15; tours cost less for seniors and children.
Underground Eureka, Arkansas, is the result of road improvements to the downtown area that required businesses to create new entrances on their second floors. The original entrances were walled off, leading to a series of basement passageways. A tour is required for viewing, and adult tickets cost $12; children under 12 enter free.
Moaning Cavern in Vallecito, California, is so deep that the entire Statue of Liberty could stand inside. While visitors can rappel into the cave, the cheapest (and least daring) option is a family-friendly walking tour, priced at $17.50 for adults and $9.50 for children ages 3 to 12.
INDIANAPOLIS CITY MARKET CATACOMBS
Indianapolis City Market sits atop a hidden network of brick catacombs. The space was originally part of Tomlinson Hall, a large building that seated 3,500 people until it burned down in 1958. The basement of arches was left behind, and now visitors ages 12 and up can tour the space for $12. The fee for 6- to 11-year-olds is $6.
SubTropolis in Kansas City, Missouri, is a giant underground business complex built in an excavated mine with limestone walls. About 1,000 people toil here every day in enterprises ranging from specialty food packaging to cloud computing to storage for postage stamps.
The city of Ellinwood, Kansas, features a well-preserved underground space from the 1800s that once housed saloons, a barbershop, and a bathhouse -- basically everything a cowboy would need. Visitors can still see some of the original items, such as the barbershop’s wallpaper and flooring. Tours are $6 for adults.
Visit the Ice Cave near Grants, New Mexico, to see natural layers of crystal-clear ice that accumulate year-round in a collapsed lava tube. General admission for a guided tour is $12. Visitors may want to bring a jacket; the ambient temperature in the one-room cave is below freezing.