In 'Hidden Cities,' urban explorer Moses Gates finds the unseen

Moses Gates is an urban planner and a visiting assistant professor at the Pratt Institute, but above all he's an urban explorer. He goes to places you might not even know exist: abandoned subway stations, sewer lines, tunnels, and caves. He's also gone atop places like the Brooklyn Bridge.

He has chronicled his travels in a book called "Hidden Cities: Travels to the Secret Corners of the World's Great Metropolises."

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"Over the last few years I've been to a lot of places, in a lot of cities, where your average tourist shouldn't be — and many more that your average tourist doesn't even know exist," he writes. "I've become part of the world of people who break into national monuments for fun, put on movie screenings in storm drains, and travel the globe sleeping in centuries-old catacombs and abandoned Soviet relics rather than hotels or bed-and-breakfasts."

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A VISIT TO ONE OF ST. PAUL'S UNDERGROUND SPACES

While preparing for today's show, host Tom Weber wanted to get a taste of Minnesota's underground. So he teamed up with geologist and University of Minnesota doctoral student Greg Brick to visit one of the metro's better-known caves, the Wabasha Street Caves. Brick has long studied the history of both natural and man-made caves throughout the Twin Cities, and documented them in his 2009 book "Subterranean Twin Cities."

The caves they visited are just a section of those that extend under the bluff of St. Paul's West Side; they're available by rent for weddings and other parties. The exact section they visited is accessible only during weekend tours, but still legal to visit with the owner's permission.

Brick first pointed out the pick marks along the walls and ceiling — all the proof you need that this cave is man-made. He explained that these caves were dug out in the 1800s and mined for their silica, a sand used largely at the time in the manufacturing of glass. Once the sand was excavated, Brick said, caves like these had cool enough temperatures to grow mushrooms and store cheese. In addition, the caves' suitability as a place to store beer during the fermenting process allowed for a boom in breweries in St. Paul during the late 1800s and early 1900s.

After prohibition ended in 1933, "a number of people got the idea to open nightclubs in these caves," Brick noted. "We're standing in one now."

After a big flood in 1965, many condemned homes along the flood plain on St. Paul's West Side were bulldozed and the debris pushed into the caves. Some of them are chock-full of sharp debris, including wood that cavers in the years since have used to build fires to combat the cool temperatures. The problem, Brick said, is that those fires use up all the oxygen in any given spot. Areas of carbon monoxide can persist, even days after the fire dies. An explorer might not realize he or she is in trouble until it's too late, especially given how hard it is to climb over the debris to get back out.

That's believed to have happened in 2004, when caves near where Brick and Weber stood were the site of a tragedy. Three teenagers were overcome by carbon monoxide; a fourth survived.

Brick said that even though he seeks out only legal areas to enter, he walks a fine line when it comes to encouraging others to be cavers.

"If I were to encourage exploration and someone were to get hurt, they'd blame it on me," he said. "And it's very rare, but when it happens people really take notice. You think of how many people are killed in car accidents, but they're so common we don't think of it anymore. But if someone dies in a cave, it's really something unusual. And then there'll be a big concern about that. I can't be seen encouraging that."

After the 2004 deaths, Brick said, city leaders studied the idea of sealing all cave entrances, but nothing came of it. "These caves are just as open now as they were back then," he said. "I've heard through the grapevine that teenagers are going in them as much as they ever were."

Classical MPR visited the caves in 2010 to record a mini-concert by the group Cantus. Here's a video of that visit:

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