Horsemen take part in the Durbar festival parade in Zaria, Nigeria September 14, 2016. It is celebrated at the culmination of Muslim festivals Eid al-Fitr and Eid al-Adha. It begins with prayers, followed by a parade of the Emir and his entourage on horses, accompanied by music players, and ending at the Emir's palace. (Photo by Afolabi Sotunde/Reuters)

Tibetan pilgrims walk outside the Sera Monastery in Lhasa, Tibet Autonomous Region, China, 11 September 2016. Sera Monastery is known as one of the “great three” Gelug university monasteries of Tibet founded in 1419. (Photo by How Hwee Young/EPA)

An employee works on a glass sphere for Christmas and New Year decoration at the “Biryusinka” toy factory, which has been producing decorations and toys for the festive season since 1942, in the Siberian city of Krasnoyarsk, Russia, November 16, 2016. (Photo by Ilya Naymushin/Reuters)

The new Toyota Concept-i concept car, designed to learn about its driver is unveiled during the Toyota press conference at CES in Las Vegas, January 4, 2017. (Photo by Rick Wilking/Reuters)

A reindeer is seen as people visit ice sculptures illuminated by coloured lights at the Harbin Ice and Snow Festival to celebrate the new year in Harbin on January 4, 2017. (Photo by Nicolas Asfouri/AFP Photo)

Shortlisted: “Two big eyes” by Miao Yong (Zejiang province, China). Damselflies look over the leaves. “I was photographing insects in a park near my home when suddenly I found two damselflies in the grass. They kept flying and it was very difficult to focus until suddenly they parked behind a leaf”. (Photo by Miao Yong/2017 Royal Society of Biology Photographer of the Year)

Yakutsk, with a population of around 270,000, holds its own title: that of the coldest city on Earth. Here: Frost-encrusted house in the city centre. (Photo by Amos Chapple/Courtesy Images/RFE/RL)

“Red Arrows” at the 2016 royal air tattoo, RAF Fairford, UK. By Jonny Williams, finalist: action. (Photo by Jonny Williams/UK National Geographic Traveller Photography Competition 2018)