My son did a high adventure where he visited caves in the midwest: Marengo, ohio caverns, and mammoth cave. The cave tour he did was 6 hours long and was 6 and a half miles. It was a tour where they got to go deeper into the cave than regular tour groups, he said the tour guide said a man has come for the last 23 years and he claims he has still seen new parts of the cave. He says he highly recommends the cave as it is very cool and a neat experience. He says both tours see "frozen Niagara" a large rock formation that looks as if it is a frozen waterfall (hence the name) the drive out there he said is boring (teenagers opinion) but is a great experience. He says do it.