Luray Caverns is the largest cave system in the Eastern United States, and listed as a National Natural Landmark.
Portions of the cave system are lighted and open to the public, for a fee of course.
The trip is certainly worth the fee though, with an organ that taps out notes on different sized rock formations like a pipe organ, underground mirror pools, and a wishing well that is supposedly filled with coins three feet deep.
Peaks and Valleys
Down and Down
Wide Open Spaces