The 110-plus caves of Carlsbad Caverns National Park were carved out not by running water and streams like many limestone caves in the world, rather these caves were dissolved by very aggressive sulfuric acid.
Explore and Discover One of the Last Frontiers in the World ... Jewel Cave Nat'l Monument, SD
NPS lessons for Mammoth Cave. The 'Clay Caves' activity is particularly good.
Discover underground caves in Southern Minnesota. Tour Mystery Cave and Niagara Cave featuring an underground waterfall. Both are nearby the top bed and breakfast town of Lanesboro, MN.
Glenwood Springs Colorado - Enjoy walking cave tours for all ages at Glenwood Caverns Adventure Park
Look at the Fit the Bill lesson for ideas to teach adaptations, specifically why birds have specific types of bills.
Cave of the Winds, Manitou Springs, CO I want my kids to see this, I went as a kid and I'll never forget it!
One Day Cave Exploration With Private GuideTour. Transportation included. Good price.
Getaways in Wisconsin: Day Trip to Cave Of The Mounds, Wisconsin
In Sweetwater, TN- The Lost Sea takes you underground starting with a bright yellow tunnel with a guided tour in the caverns and then on a boat along an underwater lake!