Trees in winter with snow and old leaves. Mammoth Cave National Park, Kentucky, USA. http://www.terragalleria.com/parks/np-image.maca0502.html Styx resurgence in winter. Mammoth Cave National Park, Kentucky, USA. http://www.terragalleria.com/parks/np-image.maca0481.html Entrance of Frozen Niagara section of the cave in winter. Mammoth Cave National Park, Kentucky, USA. http://www.terragalleria.com/parks/np-image.maca0480.html