Underground Cities in the US: Where the Secret Tunnels Actually Are

Underground cities in the US sound like a sci-fi pitch, but in a few places they are just old brick, sealed doors, and tunnels that keep showing up under everyday life.

Seattle’s sealed storefronts and saloons, Cincinnati’s unfinished subway loop that left 2.2 miles behind, and Portland’s Old Town passageways tied to the Shanghai Tunnels legend all share one messy theme: people built them for emergencies, then generations inherited them as mysteries. Add LA’s Bunker Hill tunnels and New York’s early subway showpiece, and you get a map of the country’s fear, ambition, and secrecy, all stacked under the street noise.

These are the places where the “hidden city” is real, and the story depends on what got walled up, what got reused, and what never got finished.

Underground Cities in the US Worth Knowing About

America's underground story is younger than Europe's. Most US underground cities were built between the 1880s and the 1960s, driven by fires, weather, Prohibition, and the Cold War. A few go back further. A few were built so recently they are still classified.

Seattle Underground, Washington

The original. Tour guides walk visitors through old brick storefronts, banks, and saloons sealed below the modern city. Glass-block sidewalks above let in pale light. The tour passes a bordello, a bank vault, and an opium den. Most of the underground is closed to the public for safety, but the accessible sections cover several full city blocks.

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Cincinnati Subway, Ohio

The largest abandoned subway system in the United States. Construction started in 1920 on what was supposed to be a 16-mile loop. Costs exploded, politicians changed, and the project was scrapped in 1928 with 2.2 miles of tunnel already built.

The tunnels still exist beneath central Cincinnati, mostly intact, occasionally used for utility lines and freeway support. The city has talked about reviving them for decades. So far, no one has.

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Portland Shanghai Tunnels, Oregon

A network of basement passages connecting old buildings in Portland's Old Town district. The "Shanghai Tunnels" name comes from a long-disputed claim that they were used to traffic men onto ships in the late 1800s. Historians argue about how widespread that actually was. The tunnels themselves are real, and tours run through them today.

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Los Angeles Tunnels

LA had a hidden subway. Built in the 1920s by Pacific Electric, the system was abandoned by the 1950s as cars took over. The tunnels under Bunker Hill survived as film locations, speakeasies during Prohibition, and shooting locations for movies like Mulholland Drive and Hail, Caesar! Most of them are not open to the public.

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Old City Hall Station, New York

Opened in 1904 as the showpiece of the new subway system. Vaulted Guastavino tile ceilings, stained-glass skylights, brass chandeliers. The platform was too curved for newer, longer subway cars and was closed in 1945.

Riders who stay on the downtown 6 train past the last stop can still see it as the train loops back through the station. New York's underground also hides City Hall vaults, abandoned mail-tube pneumatic networks built in 1897, and old cattle tunnels in the Meatpacking District.

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Houston Tunnels, Texas

A practical network rather than a secret one. Houston's downtown is connected by 6 miles of climate-controlled tunnels, running beneath 95 city blocks.

Tens of thousands of office workers use them daily, but most tourists don't know they exist. The system started in the 1930s as a way to connect downtown movie theaters and grew from there.

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Oklahoma City Tunnels

Oklahoma City's downtown has a similar tunnel system built starting in the 1930s. Tile and design elements vary across decades of construction. The passages serve as tornado shelters during severe weather and stay popular in the heat of summer. The network covers more than 30 city blocks.

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Salt Lake City Tunnels

Less talked about than Seattle or Cincinnati, but real. Tunnels beneath the Temple Square area have generated their share of conspiracy theories, most involving the LDS Church.

Some sections are documented as utility tunnels. Others remain officially off limits. TV shows about haunted or secret America circle back to them every few years.

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Secret Underground Cities in the US Built for War

The Cold War created a separate category. Most of these aren't tour stops. They're bunkers.

• Raven Rock Mountain Complex, Pennsylvania: Nicknamed the "underground Pentagon." A military command center built into Blue Ridge Summit, with multiple levels and capacity for thousands of personnel during a national emergency.
• Mount Weather, Virginia: A FEMA facility used to relocate the federal government during catastrophic events. Active and classified.
• Cheyenne Mountain Complex, Colorado: The famous NORAD facility, built into 2,000 feet of granite. Decommissioned as a primary command center but still maintained as a backup.
• Greenbrier Bunker, West Virginia: A relocation site for Congress hidden inside a luxury hotel from 1962 until journalists exposed it in 1992. Now open for tours.
• Camp Century, Greenland: Technically not in the US but built by the US Army Corps of Engineers in 1959. A 3,000-acre nuclear-powered base under the Greenland ice sheet. Abandoned in 1967 when shifting ice made the tunnels unstable. The radioactive waste is still buried in the ice and being slowly exposed as the climate warms.

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In Seattle, the tour guides lead you past a bordello and a bank vault, then you realize most of it is still shut off for safety, not because it is fake.

These US sealed storefronts and saloons feel similar to the ancient lost cities that sank and were found beneath the sea.

Meanwhile, Cincinnati’s subway started as a 16-mile loop, but politics and ballooning costs turned it into a half-built ghost that still sits beneath central streets.

Then Portland throws in the real-life Shanghai Tunnels maze, where the tunnels exist, but the ship-boarding story people repeat still gets argued over.

And when LA’s Pacific Electric tunnels were abandoned in the 1950s, the surviving Bunker Hill stretches became props for speakeasies, films, and whatever came next.

Abandoned Underground Cities in the US

A separate subcategory: places that were built, used, and then left.

• The original 1904 City Hall Station in New York
• Most of the Cincinnati subway loop
• The deeper levels of Seattle's underground
• Old Pacific Electric tunnels under Los Angeles
• Parts of the original Winchester Mystery House basement system, where Sarah Winchester reportedly continued construction below ground

These aren't the same as ghost towns above ground. Underground sites tend to survive in better shape, sealed off from weather and most vandals. The same preservation effect that kept the Seattle Underground intact for decades works on almost every abandoned tunnel system in the country.

How Many Underground Cities Are in the US

There is no single registry. Different sources count 10 to 30 major sites depending on how strict the definition is. Pure abandoned subway projects, downtown tunnel networks, military bunkers, mining towns like Coober Pedy don't have US equivalents at scale, but the Cold War bunker count alone is in the dozens.

Underground sites get rediscovered constantly. Most of them were originally built fast, recorded poorly, and forgotten just as fast. The Seattle Underground tour wouldn't exist if a journalist hadn't gone looking. The Cincinnati subway gets a fresh news cycle every decade. New tunnel systems show up under cities that have been mapped a hundred times.

For more on hidden and abandoned places, the secret underground cities of the wider world cover even older examples, like Derinkuyu's 18-story complex in Turkey. The story of accidental inventions covers a familiar pattern, since the Seattle Underground itself only exists because the city raised its streets and the original level was preserved as a side effect. And the Italian ghost town of Craco shows what happens when an entire city above ground gets sealed instead.

The street above changes, but the secret passages below keep rewriting the city’s past.

Want more hidden tunnels, like the Beijing bunker built for nuclear war? Read Secret Underground Cities Around the World.