Revellers celebrate "Ash Monday" by participating in a colourful "flour war", a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter,in the port town of Galaxidi, some 215 km (134 miles) north west of Athens, March 18, 2013. The revellers "fight" by throwing coloured flour, charcoal dust and powder painting until they essentially run out of supplies. (Photo by Yannis Behrakis/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)

Ingots of 99.99 percent pure silver are cast at the Krastsvetmet Krasnoyarsk non-ferrous metals plant in the Siberian city of Krasnoyarsk, Russia, June 5, 2015. Krastsvetmet is one of the world's largest players in the precious metals industry. REUTERS/Ilya Naymushin

Piper Hoppe, 10, from Minnetonka, Minnesota, holds a sign at the doorway of River Bluff Dental clinic in protest against the killing of a famous lion in Zimbabwe, in Bloomington, Minnesota July 29, 2015. A Zimbabwean court on Wednesday charged a professional local hunter Theo Bronkhorst with failing to prevent an American from unlawfully killing “Cecil”, the southern African country's best-known lion. The American, Walter James Palmer, a Minnesota dentist who paid $50,000 to kill the lion, has left Zimbabwe. He says he did kill the animal but believed the hunt was legal and that the necessary permits had been issued. (Photo by Eric Miller/Reuters)

Nasoin Akhter, 15, has her makeup done at a beauty parlor on the day of her wedding to a 32-year-old man, August 20, 2015, in Manikganj, Bangladesh. In June of this year, Human Rights Watch released a damning report about child marriage in Bangladesh. The country has one of the highest rates of child marriage in the world, with 29% of girls marrying before the age of 15, and 65% of girls marrying before they turn 18. (Photo by Allison Joyce/Getty Images)

Tibetan men get ready to perform a traditional dance during a special prayer ceremony on the third day of the Tibetan New Year celebrations in Kathmandu, Nepal, Wednesday, March 1, 2017. Tibetans follow this ritual called “sangtsol” to ask for good luck in the new year. (Photo by Niranjan Shrestha/AP Photo)

Fireplace for children, Trondheim, Norway, by Haugen/Zohar. The children of Trondheim come to sit around the fire and tell stories in this whimsical cone hut, made with materials recycled from a construction site. (Photo by Jason Havneraas/The Guardian)

Revellers celebrate during the “Bloco da Lama”, a mud carnival, in Paraty, Brazil, on February 10, 2018. “Bloco da Lama” started in 1986 by teenagers playing with mud and became a traditional event at the historical city of Paraty. (Photo by Mauro Pimentel/AFP Photo)