Superior, you say? Well, yes and no. By surface area, the greatest of the Great Lakes would correctly answer the question.

But if you consider the actual volume of water, nothing on the globe compares to Lake Baikal in southern Siberia. With a maximum depth of just over a mile, it's the deepest lake in the world. And at over 400 miles in length, Lake Baikal contains a full one-fifth of the freshwater on the entire planet. That's right — if you were to dump the H2O from all five Great Lakes into an empty Baikal, you'd have room to spare.

Scientists estimate the lake is about 25 million years old. Because of its age and isolation, the beautifully pure Lake Baikal is one of Earth's richest sources of freshwater life forms, containing in excess 2,000 unique species of flora and fauna.