The closest public accessible cave is Bluespring Caverns (link). The tour at this cavern is by cave boat. There is a gift shop where you can await the next tour. For the kids, a bag of rocks can be purchased for the sluice so they can pan for gems. Other items include sweat shirts, polished rocks, small figures of carved onyx and snacks. Figure about a 3 hour drive time for this site in the Bedford/ Mitchell area.
Spring Mill State Park (link) is outside of Mitchell, about 20 minutes from Bluespring.
Next closest is Marengo Cave (link). This cave has 2 different walking tours. A gift shop is onsite. Panning for fossils, gems and arrowheads are dependent on the package that you chose to buy. This cave has been a tourist attraction for over 100 years. About a 4 hour drive time from Lafayette.
Squire Boone Caverns (link) is about 15 miles south of Marengo. The walking tour includes 73 stairs, a waterfall and features an underground stream. Squire Boon includes a pioneer village with a grist mill, rock shop, panning for gold and several traditional craft demonstrations.
Nearby, Indiana Caverns (link) is the most recently discovered of these caves. It is also one of the longest caves known in the US, 11th in length. The tour is an hour and 20 minutes, includes both walking and a boat ride. One of the most unique features is the fossilized bones, easily seen on the tour. A 40’ waterfall is another unique feature. A total of 220 stairs are part of the tour.
Marengo, Squire Boone and Indiana Caverns form a triangle near Corydon. Modern lodging is available at Corydon (link), camping is available at O’Bannon Woods State Park (link) between Corydon and Leavenworth.