Interested in caving? Here are some good links. The Minnesota Speleological Survey (MSS) has been the local caving organization since 1963, and they have regular trips to caves, especially in southeastern Minnesota:

I've taken the tour here on several occasions, and there's something new each time:
Wabasha Street Caves, St. Paul, MN
A great website for visiting caves while you travel:

Wisconsin Speleological Society
Crystal Cave, Spring Valley, Wisconsin

If you liked SUBTERRANEAN TWIN CITIES you will also want to read this award-winning non-fiction thriller by outdoor adventure writer Cary J. Griffith:

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