Cliff

Pema Dolma, 78, opens a butter package to make a prayer candle in her cliffside home  in Chosher, Nepal. Humans have lived in caves carved out of the Mustang cliffsides for thousands of years

aylor Weidman/Getty Images

Pema Dolma, 78, opens a butter package to make a prayer candle in her cliffside home in Chosher, Nepal. Humans have lived in caves carved out of the Mustang cliffsides for thousands of years

A woman plays on the edge of a cliff on a rainy winter afternoon at Bronte beach in Sydney...A woman plays on the edge of a cliff on a rainy winter afternoon at Bronte beach in Sydney August 8, 2013. REUTERS/Daniel Munoz (AUSTRALIA - Tags: SOCIETY ENVIRONMENT TPX IMAGES OF THE DAY)

Daniel Munoz/Reuters

A woman plays on the edge of a cliff on a rainy winter afternoon at Bronte beach in Sydney, Australia