The cave is a graffiti wonder. And a lot of it is historical stuff. Lots of Civil War stuff but also things like a Mason's drawing apparently done by one or more of the Harrisons for whom Harrisonburg, VA is named. I'll get a photo of that next time I get there, as it is complicated and hard to light and I was in the middle of helping with a TV news bit when I learned about it.
Speaking of the news item, it is here and you can watch the video:
And while others are documenting all the art/graffiti, here are a few examples.