Tickets such as these were issued to passengers on the Washington Mole Way.

"Not many people have seen this," Joe Kerr said as he pushed open a rusty door, the squeak of its hinges echoing in the dark.

We were 60 feet underground, and Joe , president of a D.C. urban exploration group called Friends of Outrageously Obscure Locations, was about to show me the remnants of Washington’s first subway system. We weren’t supposed to be here — technically, we were trespassing — but I had heard so much about this subterranean wonderland that I had to see it for myself.

“Welcome to the Georgetown Mole Way station,” Joe said, clicking on a large flashlight.

The light illuminated a cathedral-like space. The walls were covered in light green tile and inset every 20 feet or so with wooden benches. A wrought-iron railing ran along the platform’s edge, interrupted at regular intervals with sliding gates. Above an ornate booth was an enameled metal sign reading “TICKETS.”

“Pretty cool, huh?” said Joe, who works for the District cleaning the lenses on speed cameras.

It was unbelievable: a crumbling, disused subway station hidden beneath busy city streets.

Construction started in 1865, just as the end of the Civil War unleashed a wave of cheap labor. Otto Witzmann, a German-born armaments manufacturer made wealthy by the recent conflict, gambled that Washington would continue to grow in size and that its residents would welcome what he called a "modern" way to travel, "free from the indignities of the common street: panhandlers, mad dogs, temperance bores, street preachers, newsboys, traffic clots, slop buckets, inclement weather and the pungent droppings of cart horses."

An ad in the Washington Panopticon newspaper sought investors: “OFFERED — An opportunity for Men of vision to join an Endeavor sure to Revolutionize travel in the District of Columbia and the County of Washington.”

Witzmann called it the Mole Way.

“The mole wasn’t held in such low esteem then,” Joe said. “Far from being seen as destructive, the mole was considered a clever, resourceful animal that could enter the earth at one point and pop up at another.”

The first 13 stations opened on April 1, 1870, and included stops near the Capitol, the White House, each of the city’s markets and an adults-only nude beach near the Tidal Basin. Also among the first stations: the one Joe and I were in, right under the intersection of Wisconsin and M Streets NW.

“I thought impenetrable bedrock made it impossible to build a Metro station in Georgetown,” I said.

Joe smiled. “Georgetown was a bustling, vital neighborhood back then,” he said. “Can you imagine anyone building a subway system in D.C. and not including a stop here?”

By 1873, 74 more stations had opened, for a total of 87, one more than the current Metro system. There was a stop at what was then called Tyson’s Farm in Fairfax County and another at a hot-air balloon depot near Sterling.

Joe and his secretive band of spelunkers have spent years mapping the Mole Way — or at least those parts that haven’t been destroyed by modern construction. About a third of it remains, its access points closely guarded secrets.

“This way,” Joe said, dropping down onto the rail bed.

I followed — and in the process dropped and broke my camera. Down the tunnel, halfway buried under a collapsed portion of the roof, was an odd, bullet-shaped vehicle. It was a train carriage!

The Mole Way’s carriages were propelled by compressed air, a system scaled up considerably from the pneumatic tubes Witzmann used in his headquarters to send messages from office to office.

We climbed inside the car. It looked as if the passengers had just left. The floor was littered with old newspapers. There were ads on the wall for “Shear Madness” at Ford’s Theater.

Signs also spelled out the Mole Way’s rules:

The Management reminds you: The consumption of foodstuffs is expressly forbidden anywhere other than in the Dining Car.

The Management reminds you: The inhalation or expectoration of tobacco products is expressly forbidden anywhere other than in the Smoking Car.

The Management reminds you: The use of harmonicas, concertinas, fiddles, banjos, barrel organs, penny whistles or other noise-producing items is expressly forbidden.

The Mole Way lasted just 13 years. Why did it fail?

“The compressed air system broke down a lot,” Joe said. “And even when it worked, it was problematical. Passengers complained that every time a train entered a station their hats would be blown off their heads — and everyone wore hats back then.”

Another problem was access. The escalator wasn’t invented until the 1890s. Instead, the Mole Way used spiral staircases that rotated like drill bits to carry passengers from street to platform and vice versa. The “spinners,” as they were called, were plagued with glitches.

Eventually, passengers got fed up and stopped riding. In 1883, Witzmann declared bankruptcy. He fled to Germany and opened a pickled herring factory. The Mole Way was abandoned, becoming little more than a forgotten footnote in Washington’s transit history.

I called WMATA to ask what the people there knew about this precursor to today’s Metro system. They claimed never to have heard of it. “This is certainly news to me,” a spokeswoman said, before asking if my call was some sort of joke.

For previous columns, visit washingtonpost.com/johnkelly.