Coldwater Cave is Iowa’s longest cave with over 17 miles of documented passages. It ranks as the 32nd longest cave in the United States.

It features over 16 miles of passages stretching from northeast Winneshiek County to southeast Fillmore County in Minnesota. The water in the cave is 47* and the spring is a tributary of the nearby Upper Iowa River.

Iowa PBS via YouTube
Iowa PBS via YouTube

How was it discovered? 

According to Iowa Magazine, in the late-1960s, after hearing about a rumor of a cave in northeast Iowa used by bootleggers during Prohibition and other stories about how farmers had been losing livestock from mysterious holes and sinkholes in the area.

So, the two University of Iowa students, David Jagnow and Steve Barnett, ventured to the Coldwater Creek Conservation Area in Winneshiek County.

Google Maps

There is only one natural entrance (Historic Entrance) to the cave and it is a water-filled spring from the base of a 100-foot-tall bluff located within the Cold Water Creek Conservation area.

At one point the state considered opening the cave for public viewing. This plan was abandoned because of the logistics of making it accessible and the environmental damage that would cause.

Iowa PBS via YouTube

According to, access to this entry requires scuba gear, and the underwater entrance is currently gated. Primary access to the cave is through a 94-foot shaft that was drilled by the State of Iowa for researcher access in the early-1970s. A second privately-owned shaft entrance was drilled in 2003 that is 188-feet deep.

Coldwater Cave Project

Coldwater Cave was designated a National Natural Landmark by the U.S. Department of the Interior in 1987.

Iowa PBS via YouTube

The duo who discovered the cave wrote and released a book about the cave, titled: A World Below: The Underwater Discovery and Exploration of Coldwater Cave. 

This cave system isn't for everyone. Due to a mix of safety, liability, and conservation reasons, if and when a group requests to go, they must have the necessary gear and experience. The Minnesota Cave Preserve owns eight preserves in S.E. Minnesota and Northern Iowa, which provides access to 36 miles of cave passages.

It's not easy to gain access to the cave even if you are given permission. You'll need SCUBA gear, no fear of traveling down a 100+ foot ladder, and you probably shouldn't be claustrophobic:

Iowa PBS via YouTube


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