The Seven Underwater Wonders of the World : Russia says "Sacred lake" is 25 million years old-the oldest lake on the planet.Lake Baikal in Russia PictureLake Baikal in Russia PhotoBeautiful Lake Baikal PictureLake Baikal in Russia PhotoIn early March, snow still blankets lake Baikal, its deep waters sealed beneath three-foot-thick ice. Over the next two months, under bright springtime sun, the