National park with caves and caverns, stalactites and stalagmites. Crystal Cave is an excellent example of a marble cavern. A half-mile loop trail leads through the cave, and there's also a steep half-mile walk to and from the cave parking area to the entrance. Because of fragile formations, the only way to visit the cave is on a guided tour. Tours are suitable for all ages. If you decide to see the cave, plan on spending about half a day traveling to the cave, walking to the entrance, and taking the 45-minute tour.