Indian commuters travel in a local train in Kolkata, India, Tuesday, February 26, 2013. Indian Railway Minister Pawan Kumar Bansal is presenting the country's rail budget for next fiscal year in the parliament Tuesday, Feb. 26, 2013. Indian railway network is one of the world's largest, with some 14 million passengers daily and some 64,000 kilometers (40,000 miles) of railway track cut through some of the most densely populated cities. (Photo by Bikas Das/AP Photo)

Onati Basque dancers go airborne as they perform Basque traditional dances while making their way to the front of Saint Mark's Catholic Church, Saturday, August 1, 2015, in Boise, Idaho. The annual Mass, conducted in English and Basque, was held at the church for the first time. (Photo by Kyle Green/Idaho Statesman via AP Photo)

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)

Two young boys kneel on stools on either side of a round table as one uses a match to this the other's cigarette, November 12, 1928. (Photo by FPG/Getty Images)

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)

Kyaiktiyo, Burma, 1978. The Golden Rock at Shwe Pyi Daw (the Golden Country), the Buddhist holy place. Hiroji Kubota writes: “I was desperate to keep a distance from America for a while; luckily, I found Burma and its gentle and compassionate people. In the spring of 1978, on the top of the hill where I took this photo, I had two Leica bodies: the one with Tri-X and the other with Kodachrome 64. Soon after, I realised that the colour one looked very colourful and was more powerful. That was my decisive moment, to become a colour photographer”. (Photo by Hiroji Kubota/Magnum Photos)

Seehund “Bruno” looks out of his transport box before making his way to the water on the beach of the island of Juist, Germany on August 14, 2013. Four young seals were released after six weeks of recovery at a rescue station in Norden-Norddeich. (Photo by Carmen Jaspersen/AFP Photo/DPA)

Pakistani civil society activists release lanterns into the sky in Lahore on December 15, 2016, as they pay tribute to victims on the second anniversary of an attack on The Army Public School in the city of Peshawar. Taliban militants attacked on Pakistani Army Public School in Peshawar, killing 151 people mostly children on December 16, 2014. (Photo by Arif Ali/AFP Photo)