We thought Mammoth Cave was worth a visit. And it does have a historic tour where you learn about how the bat guano was a critical component for civil war gunpowder. There’s not much in the way of stalactites though, so don’t expect pretty photos like Carlsbad Caverns.
Abraham Lincoln’s birthplace a few miles north wasn’t so interesting, especially when you learn that the cabin he was supposedly born in was magically reconstructed just before the inspectors came from Washington DC to determine whether it should be designated as a historic site.