Mystery Cave

Mystery Cave stretches for many miles of mapped passages, making it by far the longest cave in the state. It formed over a very long span of time as groundwater, made mildly acidic by soaking through soil, seeped into cracks in the limestone bedrock and slowly dissolved them into passages and rooms. The result is a branching underground labyrinth on several levels, discovered in the 1930s and later developed for guided tours.

Inside, visitors move through corridors and chambers decorated with the slow work of dripping water: flowstone, stalactites, and other formations built up drop by drop over thousands of years. Guides explain how the cave formed and point out its features, and part of the wonder is simply the scale and quiet of a world hidden entirely beneath the fields and bluffs above.

Among the cave's most striking sights are its pools, still sheets of water so clear and mineral-rich that they glow a deep blue-green in the lamplight. Fed by the same groundwater that carved the cave, these pools sit motionless in the dark, mirroring the ceiling and the formations above them. They are a favorite stop on the tour and a reminder that the cave is still a living, water-shaped place.

The formations that decorate Mystery Cave, the flowstone draperies and slender straws hanging from the ceiling, grow with almost unimaginable slowness as dissolved minerals harden out of dripping water. Because they are so fragile and so old, visitors are asked not to touch them; the oils from a single hand can stop a formation's growth. The cave is a museum built by water over millennia, and it is kept that way for those who come after.

Mystery Cave sits in the Driftless Area, the pocket of the Upper Midwest that the last glaciers largely missed. Instead of being scraped flat and buried in glacial debris, this country kept its rugged shape, and its limestone bedrock has been carved from below into sinkholes, springs, disappearing streams, and caves. Mystery Cave is the grandest of the region's caves, but the whole landscape is honeycombed and spring-fed.

This is the homeland of the Dakota people, whose name for the land, Mni Sota Makoce, gives Minnesota its name, and whose presence in this river-and-bluff country reaches back generations. Above ground the park protects a landscape of wooded valleys and clear trout streams, and it also holds Historic Forestville, a restored nineteenth-century village that tells the story of the settlers who followed. Cave and village together make the park a rich stop in southeastern Minnesota.

Caves are important homes for bats, and Mystery Cave shelters bats that use it for hibernation and roosting. These animals are vital to the region's ecology, eating vast numbers of insects, and they have been threatened by white-nose syndrome, a disease spread partly on visitors' gear, so the park may ask guests to follow clothing and equipment rules to protect them. Above ground the park's woods and streams hold white-tailed deer, wild turkeys, trout, and a range of Driftless-country birds.

Because the cave holds a steady cool temperature year-round, it is a welcome escape in the heat of summer and a milder world than the frozen surface in winter. The surrounding park is at its greenest in spring and summer, ablaze with color in fall, and quiet under snow in winter. Guided cave tours run on a seasonal schedule, so the warm months offer the most access, but the cave itself never really changes, holding its cool, dark constancy through every season.

The closest Boutel™ stays, so you can turn this stop into an overnight. Each is an independently owned, editorially selected place to stay.