This is in the Skyline Caverns in Front Royal, Virginia. If you keep driving right past the entrance to Shendandoah National Park and Skyline Drive you’ll come to these caverns about a mile or so down the road. The tour takes about an hour and it’s one of the few places in the world that has anthodite formations, a very rare crystal formation that only grows in limestone caverns. No one is exactly sure how they form or why the stop growing but it’s believed they can only grow in a vacuum and once the vacuum is broken they stop growing. The crystal formations are rare enough that the state of Virginia will fine you and possibly throw you in jail for breaking off so much as an inch from these formations.