Intro to Caving Tour
There are a bunch of different tours offered at Mammoth Cave, and it's pretty difficult to decide which one you want. Because the tours tend to book up quickly, it's not an option to walk into the visitor's center and decide which one you want. There is a website where you can purchase tour tickets online, and this is definitely the way to go. Look to http://www.nps.gov/maca/tours.htm for the most up to date information.
On this site there are also descriptions of the various tours. If you've never been to Mammoth Cave, there's a pretty good chance that these will mean nothing to you. Take a look at the level (some say easy while others say strenuous, the amount of time you'll be underground, and most importantly the price. The more expensive, the more experience (or so I say).
On a labor day weekend excursion with Ted we called ahead and tried to book the "Wild Cave Tour" only to discover that it was sold out for the weekend. We reluctantly bought tickets for "Introduction to Caving". The online description doesn't sound too rough, but as soon as we got into the cave, Ted and I knew that we were in for a treat.
The first task was to walk down about 300 steps into the cave. Of course that wasn't hard, but it gave some idea as to how deep we were going. Our first tough task was the "test hole". We were instructed to wiggle up through this tiny hole to make sure that we 1)had the physical strength to do it and 2)that our bodies were small enough to fit into the rest of the spaces along the tour. I made it through without much more than a scraped elbow, but man was I breathing hard. It was quite strenuous. Throughout the rest of the tour, there was a lot of climbing, crawling on knees, a few spots where we had to wiggle on our bellies, really a ton of fun. The whole time we were wearing hard hats with head lamps (we got to keep the hats after the tour!) and kneepads. They were necessary, and I would recommend buying some good quality kneepads of your own to take.
The last part of the tour is called the "keyhole". This is a tiny opening about 6" tall located across a big mudhole. You have to extend over the mud, turn your head sideways to fit it through, then wiggle the rest of your body through the hole. It was awesome! I felt like such a badass when I made it through, and I wish I had video footage.
One of the best parts of the tour was returning to the visitor's center all muddy and tired. People stared and looked frightened.