Lost World Caverns is a show cave just outside Lewisburg, with a large walking chamber, stalactites, stalagmites, flowstone, and optional rougher wild-cave tours. The cave is a National Natural Landmark and a good introduction to the karst landscape beneath the Greenbrier Valley.
The place also has a streak of odd roadside fame, including the tabloid "Bat Boy" story. That folklore is not the reason to go, but it does make the gift shop conversations more entertaining.