Cave of the Mounds
Guided walks descend past flowstone, stalactites, fossils, and crystal-lined chambers discovered beneath a quarry in 1939.
Artwork inspired by Ruth Grotenrath
The cave formed as slightly acidic groundwater moved through fractures in Ordovician limestone, dissolving passages and later depositing calcite as water released carbon dioxide. Stalactites, stalagmites, draperies, fossils, and flowstone record different relationships among rock, water, air, and time.
Tours use paved, lighted paths but include enclosed spaces, damp surfaces, and roughly 50-degree temperatures all year. Timed capacity can sell out, especially in summer. Reserve before the drive, bring a layer, and add the restored prairie and karst trails above ground to understand why surface water management matters to everything below.
- Discovered
- 1939
- Rock
- Ordovician limestone
- Tour
- Guided, paved route
Quick guide
- Look for fractures
- Passages follow weaknesses in limestone rather than forming as random underground rooms
- Best pairing
- Cave tour and surface trail
Follow a drop of water from prairie to crystal
- Look for fractures
- Passages follow weaknesses in limestone rather than forming as random underground rooms.
- Separate growth forms
- Use water direction to distinguish stalactites, stalagmites, drapery, and flowstone.
- Protect the living cave
- Touch only designated formations; skin oils and lint can alter slow-growing surfaces.
- Walk above afterward
- Prairie, sink drainage, and land care complete the groundwater story.
Good to know
Advance tickets are wise; the cave is cool, damp, and enclosed even when the surface is hot.
Notice these
- Crystal formations
- Flowstone chambers
- Karst landscape