Mammoth Cave National Park - Domes & Dripstones Tour
Read MoreIf you notice, the ceiling in this shot has a distinct green hue. This is due to algae growth. Algae is not native to the caves but rather has been carried here on the clothes of tourists at which point the light shining on the walls allows it to grow. The park service is currently taking steps to limit its growth, including installing different types of light bulbs...