Minnetonka Cave

Day 1 — June 7, 2025

We arrived with a full crew and high expectations. The plan was straightforward: start the survey at the cave entrance and push as deep as we could manage. With only one survey device between us, we split into roles and got to work, one team on instruments and sketching at the survey line, while two of us ran ahead to scout passage, locate side routes, and get a feel for the cave's overall scale.

That scouting run was humbling. Minnetonka is big. The entire tour section is a walking-height passage, and it goes on for what feels like forever. There simply isn't anything else quite like it in the state. Bats were everywhere, not clustered, but scattered throughout, hanging from the ceiling and tucked into cracks and pockets in the rock. The cave is beautifully decorated as well, and neither of us reached the end of any passage before turning back to rejoin the survey team.

We ran into some early trouble with our survey instrument, which gave wildly inaccurate readings when placed within about a foot and a half of any metal or electrical infrastructure, railings, wiring, and the like. We lost nearly two hours troubleshooting before we could recalibrate and verify the readings against a traditional compass. It was a frustrating but important lesson.

Despite the setback, we managed 741 feet of surveyed passage in our first day underground.

Day 2 — June 8, 2025

A smaller crew returned the next morning. We pushed into the largest room in the cave and finished the day at the top of the steep staircase the guides affectionately call "Stairway to Heaven." Along the way, we knocked out several side passages and pushed everything we encountered to either its conclusion or until the rock closed down too tightly to follow.

One observation that's been growing harder to ignore: this cave is full of fossils. The lighter grey limestone in particular is packed with them, horn coral, shells, and crinoids appearing at nearly every turn.

Day two added 765 feet, bringing the two-day total to 1,506 feet.

Day 3 — June 28, 2025

Three weeks later, we were back. Starting at the top of Stairway to Heaven, we worked our way through to just past Elephant's Ear, one of the cave's named features deeper in the system. The fossils continued to impress. We were told that somewhere beyond the tour's end lies a single large, fully intact crinoid fossil, and we've been keeping an eye out for it ever since.

We've been targeting 500 feet of survey per day, but the cave has been generous with us. Day three produced 806 feet, pushing the running total to 2,312 feet across three survey days.

Day 4 — August 23, 2025

This was our most productive day yet. We tackled two large offshoots that are, without question, the prettiest sections of the entire cave, heavily decorated, atmospheric, and well worth the effort to document properly. By the end of the day, we had completed the survey all the way through the tour section and just beyond its end.

The day's haul: 1,044 feet, for a new total of 3,356 feet.

Day 5 — September 6, 2025

Our final push of the 2025 season brought out our largest crew yet. While one team conducted reconnaissance deep in the final large offshoot to understand what lies ahead for next year, the main survey team finished the borehole passage and all remaining side passages except that terminal branch.

It was a day of discoveries. Down in the junction room, we found what appears to be a previously unmapped passage, roughly 100 feet long and accessed through a pit. In that same pit, we also found what looks like a connection into the passages our recon team was exploring. Everything points to next season being very interesting.

We surveyed 1,388 feet on the final day of the season, closing out 2025 with a total of 4,744 feet across five survey days, well past our original goal for the year. The only remaining section is that final large offshoot at the back of the cave. It's going to be a challenge, but we're in a good position to take it on.

Day 6 — May 30, 2026

After a winter away, we returned to Minnetonka with the back of the cave on our minds. The 2025 season had covered the entire main passage and its side passages; what remained was the long, branching network near the Junction Room, unmapped territory that the old 1990s survey had only hinted at.

We entered just after 8:30 in the morning and spent nine hours underground.

The goal was to complete the upper route (which we're calling the K Route) and make a start on the lower upper route (L Route) beyond a feature we call The Cliff. We accomplished the first objective and were well into the second when we wrapped up for the day. The L Route is full of surprises; there are numerous areas not reflected on any previous map, with side passages branching in multiple directions and a continuation that extends beyond the farthest point we reached. Those, along with several connections to the lower levels of the cave, are still waiting for a future trip.

The day's survey came to 880 feet, and with that addition, the total length of Minnetonka Cave's resurvey has crossed a milestone: 5,624 feet, more than one mile of mapped passage.

Day 6 — June 13, 2026

What was supposed to be a routine survey day turned into something we'll be talking about for a long time.

We headed into the back of the cave to work on the Silk Pajama passage—a long, complicated offshoot of the main cave system made up of multiple levels and branching corridors. The plan was simple: wrap up the upper sections and start pushing into the lower levels. Caves rarely care about your plans. Near the end of one passage, it became clear that the cave continued. Nothing about it screamed significance; it just... kept going. The problem was the rock. Above, a pile of boulders blocked the way. Below was an extremely tight crawl that no one in the group could squeeze through. We were at a dead end, or so it seemed. Rather than turn back, we started moving rocks. Digging with our hands. Shifting debris out of the crawl inch by inch. After a while, there was just enough room to get past the first pinch point. The crawl continued, narrowing further, until it ended at an opening roughly the size of a human hand. Through that hand-sized hole, the cave opened up. Not a little. Not into another crawlway or a modest alcove. It opened into a full, standing walking passage, the kind of tall, spacious corridor you'd expect to find on the tour, not buried at the end of a long series of squeezes at the back of the cave. It was hard to process. We had worked so hard to get here, crawling and contorting through some of the tightest sections in the cave, and on the other side of a hole barely big enough to see through was this. Loose rocks went through the hole first, then handfuls of dirt. Slowly, the opening grew. Eventually, there was enough space to get a head through. Then, with some effort, a body. Once inside, standing upright made the digging considerably easier, and we kept at it until everyone could follow.

The passage split almost immediately. To the right, it closed down within a short distance. To the left, it wound through the rock, gradually revealing more and more decoration, before arriving at a series of short vertical drops, almost like a natural staircase of tiered waterfalls frozen in stone. We climbed through, pushing further, and with each step, the cave grew more ornate. Then we entered the room. It was multi-leveled, with every surface blanketed in brilliant white flowstone. Scattered between the two levels were three still pools and a series of rimstone dams, those delicate, naturally formed barriers that hold back water and grow slowly over thousands of years. Everything was pristine. Nothing had been touched. There were no footprints, no old survey tape, no signs that any person had ever stood there. It was almost certainly the prettiest room in the cave, and it may be one of the prettiest I've ever seen. At the bottom of the room, a steep, flowstone-lined tube descended out of sight. We managed to get a 60-foot survey shot down it before it curved beyond our line of sight, a lead that will have to wait for a future trip. From there, we worked back into the main passage and climbed to an upper level. It held its own. A 20-foot-long pool stretched wall to wall, and beyond it, another beautifully decorated white passage continued deeper into the system. More virgin cave. More pristine formations.

Minnetonka Cave is a show cave. It has been visited by the public for decades, and the back passages have been explored by cavers who were specifically looking for more. To find a significant new section here, let alone one of this quality, is genuinely surprising. The only lead we left unchecked was that descending tube at the bottom of the flowstone room. Everything else we could reach, we surveyed. We spent 11 hours underground and covered 661 feet of passage, a modest number for a long day, but every foot of it was virgin cave. That brings the total surveyed length of Minnetonka to 6,303 feet. When the survey is complete, we believe the cave will come in somewhere around 1.5 miles, possibly more. There's still work ahead. The upper levels of the Silk Pajama passage have side passages yet to be finished, and the lower levels of the whole area remain largely untouched. Whatever is down there, the cave has already shown us it's capable of surprises.

We'll be back.

Day 7 - June 27, 2026

Not every trip underground ends with a jaw-dropping discovery. Sometimes the work is methodical, pushing leads, making sense of complicated terrain, and laying the groundwork for future progress. That's exactly what this day was.

We split up early to make the most of our time. Half the team spent the day doing reconnaissance, exploring routes to assess how much passage remained and following any leads worth checking. Meanwhile, others pushed into a section of the lower cave to start forming a plan for our next visit.

The 750 feet we surveyed today were almost entirely off the original map. The terrain was some of the most complex we've encountered in the cave, with breakdown passages threading through old collapses, low crawlways snaking between fallen rock, and routes that looped back and reconnected with the main passage in unexpected places. Navigating it required more patience than anything else.

In a few spots, we could see additional passage continuing beyond piles of breakdown, but couldn't find a safe way through. The collapses looked too unstable to disturb, so we noted the leads and moved on. It's possible we passed through areas that haven't seen visitors before, though there was nothing visually dramatic to confirm it, no pristine formations, no obvious signs of a significant find waiting on the other side.

That's the nature of breakdown terrain. It hides things. It might be hiding something here.

For now, we've done what we came to do: finished the upper sections and established a clear picture of what lies ahead. The survey is finally ready to move into the lower levels of this part of the cave, and that's where things are likely to get interesting again.

The total surveyed length of Minnetonka now stands at 7,053 feet.

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