A hand-painted brown sign on the Polar Caves walk in Rumney asked visitors to look up. It said the rock overhead weighed 80 tons, was "cracked all the way through," and rested on three contact points at the back, with about 75% of its weight "hanging over your heads."
On Sunday, October 18, the last day of the park's 2026 season, the Mysterious Hanging Boulder came down. Nobody was hurt. The sign is still there. The boulder now sits upright on the remains of the boardwalk it used to hang over.
What came down on October 18
MassLive reported that a hiker walking the trail that Sunday found the damage first. Her video showed piles of broken wooden railing, the brown "Mysterious Hanging Boulder" sign, and then a huge rectangular rock standing upright where the walkway should have kept going. She hopped across to the next section of boardwalk and went back to tell park staff. The park put out a statement around 1 p.m. the next day. The Rumney Fire Department and New Hampshire State Police both told MassLive they got no call for help about it.
The Boston Globe reported that the fallen rock blocked access to the rest of the trail. WMUR carried the news statewide the same day.
The trail sign's numbers make more sense next to the time scales behind them:
| Measure | Figure | Source |
|---|---|---|
| Weight of the boulder | More than 80 tons | Park trail sign, via NHPR |
| Share of weight over the walkway | About 75% | Park trail sign, via NHPR |
| Contact points holding it | Three, at the back | Park trail sign, via NHPR |
| Years on display to visitors | 104 | Park statement, via WBAL |
| Years since the boulders last moved | Roughly 14,000 | UNH geologist Joseph Licciardi, via NHPR |
People walked under the boulder for 104 years. That's well under 1% of the time it sat in place.
Every "cave" at Polar Caves is a gap between rocks that already fell
The park's own description explains why this matters. Polar Caves aren't caverns cut into bedrock. According to the park's About page, blocks of granite broke off Hawk's Cliff as a continental glacier thawed, and the caves are the passages left between them. The "polar" in the name refers to the cool air that comes out of those gaps. The park's Nine Granite Caves page says the same thing more plainly: the passages form in the empty space between boulders the glacier left behind.
So every named stop on the walk exists because big rocks came down and settled against each other. The park lists them as:
- Polar Pinch
- Mysterious Hanging Boulder
- The Ice Cave
- Raven's Roost
- King Tut's
- Fat Man's Misery
- The Council Chamber
- The Bear's Den
- Devil's Turnpike
- Orange Crush
- Needle's Eye
- The Lemon Squeeze
- Cool Off and Rest
The Hanging Boulder was the one feature on that list that hadn't finished falling. Its whole appeal was that it was caught partway. On October 18 it finished, and that's the same thing every other block in the boulder field did thousands of years earlier.
Why it went when it did
According to NHPR, the boulders date to the retreat of the Laurentide Ice Sheet, which once covered most of what's now Canada and all of New England. Joseph Licciardi, a glacial geologist at the University of New Hampshire, told NHPR the boulders were "probably moved last about maybe 14-something-thousand years ago."
Licciardi said he hadn't been to the park to look at the fallen rock. His best guess is that it reached a "tipping point" after thousands of years of wind, rain and temperature swings. He named frost wedging as one likely cause. That's when water seeps into cracks, freezes, expands, and slowly pries the rock apart. He told NHPR:
"It was probably more of a gradual build up of instability versus anything that would have been a dramatic cause for pushing it over the edge."
He also compared it to the Old Man of the Mountain, both in how it probably failed and in how Granite Staters reacted. "In both cases, we're looking at probably very gradual weakening of the rock over time through weathering," he said. The Old Man collapsed on May 3, 2003.
The Boston Globe spoke with geologist Jan Earle, who said erosion and added weight could have tipped the boulder. The Globe described it as balanced with part of its weight on its base and part hanging out over the trail. The Globe also reported that the park declined to comment further on the cause.
Both geologists point to slow wear over a very long time, with no single dramatic trigger. In NHPR's report, Licciardi put it this way: "We live on such a dynamic planet. And that includes the rocks."
The park's next decision
Because the rock fell on closing day, the park has the whole off-season to respond. Here's the park's statement, as quoted by NHPR:
"During the off-season, Polar Caves will assess the site to determine appropriate next steps. The safety of our guests and employees continues to be our highest priority."
The park also said it looks forward to "welcoming everyone back for the 2027 season." In the statement MassLive published, the park added that it is "committed to ensuring that Polar Caves continues to be a fun, memorable and safe family attraction for generations to come."
The calendar works in the park's favor. In 2022, the Union Leader described the usual schedule: weekends in May and early June, daily from late June through August, then fewer days in September and October. If 2027 follows that pattern, the park has a full winter and early spring to decide what to do with the stretch of trail the boulder now blocks. The park's calendar page is where 2027 operating dates will appear.
The same Union Leader feature laid out the park's history. Edwin Collishaw opened the attraction in 1922 and soon sold it to the Prescott family, who still owned it when the article ran in May 2022. Today the park describes itself as family-owned and operated since 1922.
Most of what draws families up the hill is untouched by the fall. The park's homepage lists the animal exhibit with fallow deer and ducks, the boulder maze, nature trails, the Main Lodge Gift Shop, the Maple Lodge Interactive Center and the Baker River Mining Sluice, along with the boulder caves themselves. The Hanging Boulder was one stop on a longer walk. That stop is now the stretch of smashed boardwalk the park plans to assess during the off-season.
For more on what's changing around town, see our look at what the Rattlesnake Mountain fire changed for Rumney Rocks and the two counters that run Rumney's Main Street.
If you grew up walking under that boulder, or you've taken every visiting relative to Polar Caves, I'd love to hear your story. The memories people attach to places like this are part of what makes a Rumney home feel like home. And if you're wondering what your own Rumney property is worth heading into 2027, Juli Kelley can walk you through it. Start with a free home valuation, or browse more about the town on the Rumney neighborhood page.
