Two boys look out from the Mangueira slum towards the Maracana Stadium that is hosting the Rio's 2016 Summer Olympics opening ceremonies, in Rio de Janeiro, Brazil, Friday, August 5, 2016. (Photo by Leo Correa/AP Photo)

A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

British visitors wearing Bavarian costumes walk ahead the opening of the traditional Bavarian Oktoberfest festival at the Theresienwiese in Munich, southern Germany, on September 20, 2014. Germany's world-famous Oktoberfest kicks off with millions of revellers set to soak up the frothy atmosphere in a 16-day extravaganza of lederhosen, oompah music and, of course, beer. (Photo by Karl-Josef Hildenbrand/AFP Photo/DPA)

A combination photo shows some of the colourful doors seen in Rabat's Medina and Kasbah of the Udayas, September 2014. UNESCO made Rabat a World Heritage Site two years ago and media and tour operators call it a “must-see destination”. But it seems the tourist hordes have yet to find out. While visitors are getting squeezed through the better-known sites of Marrakesh and Fez, the old part of Rabat - with its beautiful Medina and Kasbah of the Udayas - remains an almost unspoiled oasis of calm. Smaller and more compact, its labyrinths of streets, passages and dead ends are a treasure trove of shapes and colours, of moments begging to be caught by the photographer's lens. (Photo by Damir Sagolj/Reuters)

A guard stands at Dityatki checkpoint, marking a 30 km (18-mile) zone around the Chernobyl nuclear power plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

English singer and songwriter Anne-Marie performs on stage during day two of Capital's Jingle Bell Ball with Seat at London's O2 Arena on December 8, 2019. (Photo by Isabel Infantes/PA Images via Getty Images)

Bathers brave the cold waters of the North Sea as they take part in the annual Boxing Day dip at Redcar Beach on December 26, 2019 in Redcar, England. The event attracts hundreds of people each year who take to the cold water wearing fancy dress as they help to raise money for a number of charities. (Photo by James Glossop/The Times)

A woman sits behind a bicycle on a cold winter morning in New Delhi, December 31, 2019. (Photo by Anushree Fadnavis/Reuters)