Hiking in the Black Hills is a staple past time for many locals, but for a some, the most interesting trails aren't the ones best marked or the safest.
Hidden within the ranks of avid mainstream hikers are a subculture of subterranean enthusiasts spending their time wandering through abandoned mines.
It's hiking taken to a whole new level. If hiking is basic arithmetic, then snaking through holes in the hills is calculus.
"The mines here in the Black Hills are quite popular with hikers," said hiker Matthew Lynn. "I've hiked maybe a dozen of them."
Part of the intrigue is generated by rusty, old mining structures, that seem to come alive with every eerie gust of wind.
"There's just a lot of history and it's neat to learn about these places," Lynn said. "You see old black and white photos of mines like this and it's just nice to come out and have a look at them."
While the buildings are interesting, the mine itself is altogether a different experience.
"It's just so peaceful and quiet in here," Lynn said, standing deep within one of the more popular hiking mines. "It's dark. It's an escape from everyday life."
Just because it's a popular hike, doesn't mean it's safe.
"Mines are not a good place to play," said Frank Carroll.
Carroll is retired now, but spent 31 years with the U.S. Forest Service and is widely respected when it comes to matters in the Black Hills.
"For the most part mines are wonderful," Carroll said. "They're fun to visit, very interesting to look at, but they can also be dangerous."
Carroll says there are thousands of mines in the hills, most of which are abandoned. In other words, they haven't seen any maintenance for years, if not decades.
Last month an Arizona a prospector fell through a mine shaft and spent days without food or water, fending off rattlesnake. That's an experience Lynn and other hikers hope to avoid.
"You have to be careful where you step and what you're getting yourself into," Lynn says, stepping over a what looks like a puddle. Concealed below the surface of the puddle is a mine shaft going who knows how far down. "Some of these tunnels can collapse."
Despite the inherent dangers, Carroll and Lynn both agree, mines in the Black Hills should remain open to the public.
"Look at the outside, dream of about what it must have been like on the inside, but quell your curiosity and don't go into holes you haven't been in before," Carroll said.
Still, for people like Matthew Lynn and others like him, some curiosity can't be quelled.
There are some efforts to close the most dangerous mines. Even with the obvious dangers, Carroll says there hasn't been a search and rescue effort in a local mine in nearly two decades.