Cracked Ice, Lake Khövsgöl

It's recommended that ice be at least 4 inches thick for an average-size person to walk on it. In places like northern Mongolia, where winter temps regularly dip deep below zero, ice thickness tends to skate right by that minimum requirement—but hairline cracks may still form even in sturdy ice, as shown in this close-up of Lake Khövsgöl's frozen surface. The lake is Mongolia's largest by volume, and due to its freshwater composition, it freezes much more readily than the nation's numerous saline lakes.