Two carnival revellers masquerade as Leonardo da Vinci's painting “Mona Lisa” pose in St. Mark's Square in Venice, Italy, Sunday, January 31, 2016. Carnival-goers in Venice are being asked by police to momentarily lift their masks as part of new anti-terrorism measures for the annual festivities. (Photo by Domenico Stinellis/AP Photo)

Chinelos (traditional costumed dancers) perform in front of San Andres Ocotlan church as part of continuing festivities to welcome the new year in Calimaya, Mexico on January 4, 2016. (Photo by Arturo Hernandez/Demotix/Corbis)

Schoolchildren perfom during celebrations to mark 35 years of Zimbabwe's Independence at the National sports stadium in Harare, Saturday, April 18, 2015. President Robert Mugabe, 91, the central figure in Zimbabwean politics 35 years after Independence from Britain, has led the country since 1980. (Photo by Tsvangirayi Mukwazhi/AP Photo)

Nestled among the cocoa plantations of western Ivory Coast is a gold mine that does not feature on any official maps. It is not run by an industrial mining company, nor does it pay taxes to the central government. The unlicensed mine is a key part of a lucrative business empire headed by the deputy commander of the West African nation's elite Republican Guard, United Nations investigators allege. Here: A gold prospector sits and eats close to a soldier at a gold mine near the village of Gamina, in western Ivory Coast, March 18, 2015. (Photo by Luc Gnago/Reuters)

Female North Korean traffic police officers gather in front of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, February 16, 2013. North Koreans turned out to commemorate what would have been the 71th birthday of Kim Jong Il who died on December 17, 2011. (Photo by David Guttenfelder/AP Photo)

A man rows a boat on the Dal Lake as a woman holds an umbrella during snowfall in Srinagar February 19, 2015. (Photo by Danish Ismail/Reuters)

Yang Juan, an employee at Goopal Group, takes a nap in her seat after lunch, in Beijing, China, April 21, 2016. Office workers sleeping on the job is a common sight in China, where a surplus of cheap labour can lead to downtime at work. But in China's technology sector, where business is growing faster than many start-up firms can hire new staff, workers burn the midnight oil to meet deadlines and compete with their rivals. Some companies provide sleeping areas and beds for workers to rest during late nights. (Photo by Jason Lee/Reuters)

Indian commuters wade through floodwaters during the continuous rain shower in Calcutta, India, July 10, 2015. A monsoon shower hit the city and disrupted daily life. The Indian monsoon, takes place between May and September. (Photo by Piyal Adhikary/EPA)