We visited Mammoth Cave in Kentucky. It was a big surprise. Before visiting, I had no idea that such a large and complex cave system existed in the states. The great thing about Mammoth Cave is that it is suitable for basically everyone. They have hard core caving expeditions, if you want to try that, but they also have some relatively easy walks. I visited here after badly dislocating my ankle and still really enjoyed the trip.
Mammoth Cave is a great example of one of the wonders of America. It is just so unexpected. It is an amazing natural wonder, but it also has history and stories to tell and fantastic , unique experiences.
Kentucky is also a great place to drive.
This is one of those places that is great to explore and find hidden treasures.
I would rate 8.4.