Know about fantastic conical hills in central Turkey have been made even more extraordinary by local cave dwellers. A mountain-ringed lake in southern Siberia, the deepest on Earth, contains one-fifth of the world’s fresh water. Natural limestone dams cut across a river to form a chain of glassy lakes high in the Hindu Kush Mountains. Volcanic eruption that killed 36,000 people, a new island has risen out of the sea. And many more!