The stunning image is of a rainbow cloud, captured above Mt Everest by Oleg Bartunov whilst on an expedition in the Himalayas, Nepal. The amazing rainbow effect is created when tiny ice crystals in the water vapour of the clouds reflect the sunlight.
Explore the ancient caves of Hang Son Doong, Vietnam. Hang Son Doong is one of the largest caves in the world and features a fast-flowing underground river. For spelunkers, exploring Hang Son Doong is the equivalent of scaling Mount Everest.