A heat-stressed koala waits as a resident pours water on its back on December 19, 2015 in Adelaide, Australia. Adelaide is experiencing an extreme heatwave, with temperatures reaching over 40 degrees for five consecutive days. (Photo by Morne de Klerk/Getty Images)

Mike De Butts adds the finishing touches to a giant Baobab Tree sculpture entitled “Under the Baobab”, outside the Southbank Centre on May 24, 2012 in London, England. The Pirate Technics' installation is made from a selection of brightly coloured fabrics from around the world, and is part of the Southbank Centre's “Festival of the World” exhibition, which includes a series of large scale pieces of art that will be in place around the Southbank centre over the Summer. (Photo by Dan Kitwood)

A member of the “Castellers Minyons de Terrassa” adjusts her belt before forming a human tower or ÒcastellÓ during the festival of the patron saint of Barcelona “The Virgin of Mercy” at Sant Jaume square in Barcelona, Spain, September 20, 2015. The formation of human towers is a tradition in Catalonia dating back to the 18th century. (Photo by Susana Vera/Reuters)

It is already one of the world’s most iconic cities, but this incredible collection shows how much Paris has changed over the course of the past century. The collection, by French photographer Julien Knez, shows Paris in the 1940s against a backdrop of how the same places look today. Knez says he put the striking collection together to celebrate the 71st anniversary of the city’s liberation from Nazi control in August 1944. Here: Soldiers outside the Hotel De Ville in the 1940s. (Photo by Julien Knez/Caters News)

A man rides a horse through flames during the annual “Luminarias” celebration on the eve of Saint Anthony's day, Spain's patron saint of animals, in the village of San Bartolome de Pinares, northwest of Madrid, Spain, January 16, 2017. (Photo by Paul Hanna/Reuters)

Iraqi soldiers from 9th Armoured Division give drops of water to a dehydrated child rescued earlier by soldiers at the frontline, during the ongoing fighting between Iraqi forces and Islamic State militants near the Old City in western Mosul, Iraq June 13, 2017. (Photo by Erik De Castro/Reuters)

Members of the Uniao da Ilha do Governador Samba School perform during the first day of the Special Group Samba Schools parade of Carnival at the Sambadrome in Rio de Janeiro, Brazil, 07 February 2016. (Photo by Luiz Eduardo Perez/EPA)

Penitents wearing masks, known locally as “Morions” take a selfie during the start of Holy Week celebrations in Mogpog, Marinduque in central Philippines March 21, 2016. The Moriones is an annual festival held on Holy Week on the island of Marinduque, Philippines. The “Moriones” are men and women in costumes and masks replicating the garb of biblical Roman soldiers as interpreted by local folks. (Photo by Erik De Castro/Reuters)