29. Mammoth Cave, KY

Mammoth Cave offers the most extensive cave system in the United States, and they are still looking for undiscovered areas. There are a number of tours offered every day, and you can pick and choose based on your time-frame, sense of adventure, and claustrophobia. I wouldn't worry too much... they're not going to take you on a tour that is going to kill you.They're usually pretty good about keeping tours to the public separate from organized school tours, so you can probably avoid the distraction of large groups of obnoxious kids. On the other hand, kids do tend to ask some interesting questions that escape the minds of many adults, so it's not always a bad thing. At the visitor's center, they will have a list of each tour, its length, its price, and a description of what you will see on each one. This will make your decision easy. I personally would like to go back and take their more adventurous full-day tour. On this tour, you are expected to pack a lunch and will explore many different areas of the cave. You would be climbing through very small spaces and very dark areas using ropes and one of those cool helmets with the flashlight on front. Enough to make some people go crazy I'm sure, but there's no turning back once you start.In the surrounding area, you will find people to be ridiculously friendly. Kentucky prides itself on its friendliness, and I found no reason to think otherwise. Their accents are comforting, their females beautiful, and their smiles are welcoming. Check it out. At the very least, you can go back home and tell people you went spelunking... how cool is that?