Ukrainians pour water on each other on a street in Lviv, Ukraine, 02 May 2016. The tradition of pouring water was an ancient spring ritual of cleansing on first Monday after Orthodox Easter. (Photo by Mykola Tys/EPA)

In this Monday, October 5, 2015 photo, a thick blanket of early morning fog partially shrouds the skyscrapers of the Marina and Jumeirah Lake Towers districts of Dubai, United Arab Emirates. Dubai's rapid transformation from a desert outpost into one of the world's most architecturally stunning cities is mapped out in the Marina. Where just 15 years ago there was empty, flat land, today a bustling neighborhood thrives centered around a canal and an impressive skyline that pierces through the clouds. (Photo by Kamran Jebreili/AP Photo)

Participants wearing fantasy costumes attend the 4th Hero Festival in Marseille, France on November 11, 2017. The 4th Hero Festival edition has attracted all sorts of people to role play their favourite characters from all kinds of movies and comic book legends. (Photo by Jean-Paul Pelissier/Reuters)

The photography of Art Wolfe covers the globe, capturing landscapes, wildlife, and cultures from every continent; here he talks through a selection of his favourite images. Art Wolfe is an American photographer and conservationist. His photographs have been noted by environmental advocacy groups for their “stunning” visual impact. Here: Snowy owlets (Bubo scandiacus), Arctic National Wildlife Refuge, Alaska, USA. (Photo by Art Wolfe/Art Wolfe Stock)

Planes land in fog at Heathrow Airport, west London, as heavy fog covers a many parts of the south east, on April 1, 2014. (Photo by Steve Parsons/PA Wire)

An Iraqi Muslim woman walks past Christmas decorations for sale in the Shiite holy city of Najaf on December 17, 2015. (Photo by Haidar Hamdani/AFP Photo)

Competitors in the Big Air challenge at the Proryv-2016 festival of extreme sports in Moscow, Russia on March 27, 2016. (Photo by Xinhua/Rex Features/Shutterstock)

“Warming up”. This photo I capture in the early afternoon, the animal species of lemurs fly. Photo location: Sambas, West Kalimantan, Indonesia. (Photo and caption by Hendy Mp/National Geographic Photo Contest)