Mammoth Cave National Park

I second the recommendation for Mammoth Cave National Park, unless caves aren't your thing.

If you want waterfalls, you'll have better options staying in Tennessee. Burgess Falls and Cummins Falls are both about 1.5 hours east of Nashville, and can easily be combined in a single day as they are less than half an hour apart (just did that last weekend, about a 7 hour trip total). Burgess Falls is a BIG waterfall, among the most impressive I've seen in the Southeast, though you really need to go to the base to properly appreciate it.

Thanks we will be there 5 days so we will do both caves and falls we are early risers so we will be on the road and back early to still enjoy the sites of Nashville. Thanks again

We loved the Mammoth Caves when we stayed in Bowling Green hope to do it again soon.

The Corvette Museum is very interesting whether you own a Corvette or want to own a Corvette. Displays change throughout the year. There is a small cafe in the museum. In downtown Bowling Green stop at Mariah's Food & Spirits just opposite the square. Very interesting place and good food. If it is still seasonal (like fall) head for the Johnson Orchards where you can buy all kinds of fresh apples plus lot of side products. The downtown area of Bowling Green is historical and worth a visit. Western State University is the place to go if there is a major sporting event in town that weekend.

This won't help the original poster, but for those visiting next month, the corvette museum will be free during November for all military personnel, veterans, firemen, and police.