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:
Minnesota Speleological Survey


National Speleological Society

A great website for visiting caves while you travel:
I've taken the tour here on several occasions, and there's usually something new each time:
Wabasha Street Caves, St. Paul, MN
Just an hour east of St. Paul is:
Crystal Cave, Spring Valley, WI