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4 Secret Subways Hiding Underground

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It seems impossible to think that a city could have an underground rail system that most people don't even know about. But that's the case with these four secret subways hidden beneath the bustling streets of some of America's biggest cities.

1. The Wet & Windy City

Starting in 1899, the Illinois Telephone and Telegraph Company dug under most of downtown Chicago, creating nearly 62 miles of tunnels, six feet wide by seven and a half feet tall. Their original intention was to house telephone cables, but the company also installed tracks to make getting around easier. Spotting an opportunity, they renamed their business The Chicago Tunnel Company in 1906 and became an underground delivery service instead.

At their peak use, the tunnels buzzed with around 150 small locomotives, hauling 3,300 miniature train cars that delivered 600,000 tons of freight every day. Using special elevators connected to the tunnels, businesses like Marshall Field's would get new clothing and shoe shipments from the rail, but delivering coal for furnaces was the company's bread and butter. However, by the late-1940s, most buildings were using natural gas for heat and those still using coal were getting it by truck, which was much cheaper. Business declined until the company went bankrupt, and the tunnels were sealed in 1959. Shortly after, scrap metal thieves cleaned out the tunnels, including steel doors that were meant to close off the passageways that ran under the Chicago River.

The rails were virtually forgotten until 1992, when a pile driver in the Chicago River hit a freight tunnel wall. A small crack eventually became a 20-foot hole, allowing over 100 million gallons of water to flood the tunnels. Many downtown buildings still had basement connections to the railway, so as the water rose underground it flooded these buildings too, ruining stock in storage rooms, shutting down the Chicago Mercantile Exchange and Board of Trade, and shorting out electrical power for blocks. Days later, the hole was repaired and the water was pumped out. The clean-up cost and estimated damage to downtown businesses was more than $1 billion. Since then, many sections of the tunnel have been closed off, while other branches have come full circle—they're once again being used to house telecommunication wires.

2. The Subway You Paid For (And Probably Didn't Know It)


Once called "the shortest and most exclusive railway in the world," the U.S. Capitol Subway—AKA "The Senate Subway"—is a little-known secret to most Americans. Initially built in 1912, a small, two-line monorail system linked the Capitol building to the Russell Senate Office Building just 1/5 of a mile away. The open-air cars held 18 people in wicker seats, took 45 seconds to make a one-way trip, and were known to travel back and forth up to 225 times a day when the Senate was in session.

mccain-subwayOver the years, the line has expanded to all the Senate Office Buildings, as well as to the House Office Building, allowing every member of Congress to reach the Capitol with ease. The old cars were upgraded in 1965 with new models that include upholstered seats and windshields, most of which are still in use today. In 1993, the cars on one line were replaced with sleek, fully enclosed cabins, and feature an automatic, driver-less system, which normally performs quite well. However, in May 2009, the train broke down, stranding Senators Voinovich, Lieberman, Alexander and McCaskill between stations. McCaskill let the world know via Twitter that their train had stalled. They were rescued shortly after, but McCaskill was still a little leery, tweeting that it "takes longer, but I think I'll walk."

And in case you were wondering, you don't have to be in Congress to ride the Senate Subway, but you do need special clearance to do so.

3. If You Can't Beat City Hall, Go Under It

beach-subway-2New York City's streets were becoming an overcrowded, dangerous place to be. So in 1866, Alfred Beach, scientist, inventor, and publisher of Scientific American, came up with a plan to shuttle people around underground. The concept worked just like the pneumatic tubes for the drive-up teller at your local bank, with a giant fan pushing and pulling the train cars from station to station. But there was one big roadblock to Beach's plan: a powerful, corrupt politician named William "Boss" Tweed. Tweed was accepting bribes and kickbacks from everyone in New York City, including, it's speculated, the businesses that ran private streetcars. Because Tweed had a vested interest in keeping the streetcars going above ground, he fought any proposals to develop public transportation down below. Knowing this, Beach asked for and received permission to build a tunnel for delivering mail via pneumatic tubes.

In a gutsy move, Beach used his permit for the mail tunnel as cover to build a working prototype of his pneumatic subway system. The project was constructed in secret, mostly at night, and cost Beach $350,000 of his own money. When it was finished, the subway featured one velvet-seated wooden train car riding inside a 9-foot diameter brick tube that ran 300 feet down the length of Broadway—right in front of City Hall. The subway started at a lavish station that featured painted frescoes, goldfish swimming in a fountain, and a grand piano to complete the upscale ambiance.

beach-subwayAfter a grand opening celebration in 1870, thousands visited Beach's subway for a ride. Thanks to public enthusiasm, the state legislature approved funding to start building on a grander scale. But Boss Tweed and the governor aligned to veto the bill, and they succeeded in shutting down the subway a year after it opened. The tunnel was eventually closed and sat forgotten until 1912, when workers adding a new branch to the Brooklyn-Manhattan Transit (BMT) line accidentally broke through the tunnel wall. They found what was left of the station and the wooden car, but it had deteriorated beyond recovery. A few photos of the car were taken before it was destroyed to make room for the new subway line.

4. The Subway That Never Was

During the first part of the 20th Century, Cincinnati was one of the largest cities in the country, with a growth rate nearly the same as Chicago and New York City. And like those cities, Cincinnati had a problem with dangerous, busy streets. So in 1916, a 16-mile mass transit system was proposed to alleviate the congestion. The project included aboveground and underground rails with much of the latter to be constructed by tearing up the Miami and Erie Canal, a man made waterway that had fallen into disuse.

$6,000,000 in bonds were approved in April 1916, but America had entered World War I just eleven days before, and the federal government soon put a freeze on all bond issues. When the war was over, the price of steel and concrete had skyrocketed, so the original $6,000,000 was now insufficient. A modified plan eliminated some of the original 17 stations and cut the track down to six miles, servicing only the western half of the city. With the new plan, construction began in 1920 and lasted until 1925, when the $6,000,000 ran out. During that time, two miles of 26-foot wide subway tunnel were built where the canal had been, and then covered by a new street, Central Parkway, creating a major thoroughfare for aboveground traffic. Until more money could be raised, there were no tracks or train cars, but the infrastructure was in place for the subway's eventual completion.


While city government argued over what to do next, the Stock Market crashed in 1929, World War II stalled the project, and by the 1950s, America was in love with its automobiles, so the demand for mass transit dried up. Today, the tunnel sits, unused and unfinished for nearly 85 years. The entrance to the grand staircase that leads to the tunnel has been closed and most of the aboveground stations have been torn down. There's really very little evidence that the tunnel even exists, which is perfectly fine to some people embarrassed by the project's history.

Over the years there have been numerous attempts to find some use for the tunnel, but none have been successful. Most recently, in 2002, a proposal for mass transit was again considered, but the idea was voted down.
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Does your city have any legends of secret, underground passages? Are there tunnels in your neighborhood you've always wanted to explore? Tell us about them in the comments below.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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