Laurel Caverns is Pennsylvania’s longest cave and is all natural, following the slope of the mountain. The guided tour takes about an hour and visitors go roughly 300 feet into the cave. The main entrance is the only man-made section of the cave, which is why echoes can be heard. Once you enter the caverns, the temperature drops to its year-round average of 52 degrees. Laurel Caverns is unusual since it is not a limestone cave, but rather occurs in sandstone made up of silica grains cemented together with calcium carbonate.