The largest cave owner in the U.S.
I was surprised to see this on HN! A story, if you'll permit...I visited two of Ackerman's caves (Spring Valley and Temple of Doom) in May of 2002. It was a few days shy of high school graduation and summer was starting to arrive in Minnesota.My future Firebase co-founder, Andrew, and our high school classmate, Bob, made the drive down there one Saturday. Bob had been a sort-of pupil of Ackerman's, helping him explore and map the various caves he had found.The day started innocuously enough with a visit to the main Spring Valley Cave that the article references as being previously owned and equipped to give tours. Bob took us off the steel gantry-ways and into some side passageways and chambers that were rarely trafficked.It was the second cave, Temple of Doom, that was the more, ah, interesting experience. It has only recently been discovered and wasn't fully mapped yet. We popped open a man-hole cover in the middle of a corn field and dropped down a ~50 foot steel ladder. From there the cave descended in a spiral, with the passageway barely able to fit a human. Bob, typically the most composed human I knew, occasionally burst into fits of expletives, followed by silence. "Uhhh... Bob, everything OK?". Descending a 20-30 degree downward slope with inches to spare on every side, occasionally getting stuck, and with no way to turn-around was hair-raising.After some undetermined period of time we finally got to the bottom of the spiral. At this point, Bob announced we could either brace ourselves between two sheer, very wet, rock faces and climb up ~100 feet without ropes, or go back the way we came. So... up the rock faces we went. Fortunately nobody slipped.I can still viscerally feel the elation of emerging into bright afternoon sun of the corn field, grateful and relieved to be uninjured.This was one of the several intense and bonding experiences Andrew and I had together, and perhaps contributed to why we kept working together despite some early startup failures.As for Bob, he kept on spending time with Ackerman, until one day he was buried alive by a cave entrance collapse. Ackerman dug him out with a backhoe, but he was a little more wary of caving after.