[The Conversation Africa] The Earth's surface is splotched with 117 million lakes. Some are scarcely more than ponds, while others are so big they can be seen from space. At 395 miles long, 49 miles wide and just over 1 mile deep, Lake Baikal in Siberia is one of the world's largest and it's home to 2,500 species, including the Baikal seal - Earth's only species of freshwater seal.
