Crystal Cave is a cave in Wisconsin

Wisconsin

Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

's Pierce County

Pierce County, Wisconsin

Pierce County is a county located in the U.S. state of Wisconsin. As of 2010, the population was 41,019. Its county seat is Ellsworth. Pierce County is part of the Minneapolis-St. Paul-Bloomington, MN-WI Metropolitan Statistical Area .-Geography:...

, approximately 1 mile southwest of Spring Valley

Spring Valley, Wisconsin

Spring Valley is a city in Pierce and St. Croix Counties in the U.S. state of Wisconsin. The population was 1,189 at the 2000 census. The village is located mostly within the Town of Spring Lake in Pierce County. Small portions also lie in the Town of Gilman, also in Pierce County, and the Town of...

. Discovered by accident in 1881 by William Vanasse, the cave was formed by underground erosion of the Prairie du Chien dolomite

Dolomite

Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....

. During the school year, the cave is a popular destination for school field trips.
The cave is accessed by a series of steps and ramps that allow visitors to descend over 70 feet.