Photo by Stephanie Suen in Fern Cave
Photo by Stephanie Suen in Fern Cave
Photo by Stephanie Suen in Fern Cave
Photo by Calvin Sanders: Ahrlin Baumin in Goldfinch Cave
Photo by Michael Straßburger, taken 534m deep in the Braunschweig-Lüneburg salt mine in Germany
Photo by Stephanie Suen in Mundy Cave
Photo by Stephanie Suen in Mammoth Cave