Cave of the Mounds (Visit this link)

The most significant cave in the upper Midwest, a National Natural Landmark, Cave of the Mounds lies just off U.S. Highways 18/151 in Blue Mounds, WI. The United States Department of the Interior and the National Park Service designated Cave of the Mounds a National Natural Landmark because the site possesses "exceptional value as an illustration of the nation’s natural heritage and contributes to a better understanding of man’s environment".

Commonly referred to as the "jewel box" of America’s major caves, for the variety and delicacy of its formations, Cave of the Mounds is recognized by the Chicago Academy of Sciences as "the significant cave of the upper Midwest".

Fun Fact- The Cave has the same temperature everyday, all year long! 50 degrees F.

A guided tour of the Cave takes you past a varied collection of colorful stalactites, stalagmites, columns and other formations. The main cavern began forming over a million years ago as acidic water dissolved the limestone bedrock far below the surface. As Cave of the Mounds staff like to point out, geologic time is mind-boggling. It is difficult to imagine the time it took for the large caverns to be dissolved within rock that is itself believed to be over 400 million years old!

A lower meandering portion of the Cave was formed by the rushing water of an underground stream. The contrast between chemical and mechanical processes of cave formation is one of the geologic lessons illustrated on the tour.

People who come to the Cave of the Mounds in the summer appreciate the constant 50-degree temperature. They also like the park-like grounds with picnic areas and rock gardens. Winter visitors can take advantage of the Cave’s comparative warmth because the Cave is open in the Winter on weekends and during the week by advance reservation.

http://www.caveofthemounds.com