We've been to Mammoth Cave NP several times. I’ve always enjoyed doing the Historic Tour in the morning, get lunch, then take the Domes and Drip Stones tour in the afternoon. I use the NP website to reserve the tours before arriving so I can pick the times. The Historic Tour, as its name suggests, gives you a lot of background on the cave and its history. The entrance to the Domes and Drip Stones is really dramatic. The Domes and Drip Stones tour involves a short bus ride from the Visitor Center to a different section of the cave. They have surveyed more than 405 miles of cave passage so its interesting to visit another section.