In southern Siberia is the world’s largest freshwater lake, Lake Baikal, which is covered by ice in this image. The lake contains about 20 percent of the world’s fresh surface water, which is more than all of the North American Great Lakes put together. Baikal water is extraordinarily clean and transparent and harbors unique life-forms. At twenty-five million years old, this remarkable lake is also the oldest in the world. In 1996 it was listed as a UNESCO World Heritage site. The lake is surrounded by mountain-taiga landscapes, which are also protected to preserve their natural state. March 14, 2017.