Imagine the surprise of young lumberjack, Ho Khanh, a native of Vietnam's then-sleepy Phong Nha township, when he saw enormous, ethereal columns of fog billowing out of the ground, like the earth ...

A vast subterranean cave system in southern France, near Avignon, is rewriting what we thought we knew about prehistoric human exploration. The Saint-Marcel cave network, stretching over 40 miles, ...