A photograph released to Reuters on August 22, 2014 shows the remains of an ancient Mayan city in Lagunita May 30, 2014. Archaeologists have found two ancient Mayan cities hidden in the jungle of southeastern Mexico, and lead researcher Ivan Sprajc, an associate professor at the Research Center of the Slovenian Academy of Sciences and Arts, says he believes there are “dozens” more to be found in the region. (Photo by Reuters/Research Center of the Slovenian Academy of Sciences and Arts)

Visitors watch as Grigory Broverman, a member of the Cryophile winter swimmers club, pours a bucket of cold water over his 6-year-old daughter Liza during a flash mob, part of a celebration of Polar Bear Day at the Royev Ruchey Zoo in a suburb of the Siberian city of Krasnoyarsk, Russia, November 29, 2015. The air temperature was around minus 5 degrees Celsius. (Photo by Ilya Naymushin/Reuters)

Frida, a rescue dog belonging to the Mexican Navy, with her handler Israel Arauz Salinas, takes a break while participating in the effort to look for people trapped at the Rebsamen school in Mexico City, on September 22, 2017, three days after the devastating earthquake that hit central Mexico. (Photo by Omar Torres/AFP Photo)

Indian mourners perform a cremation on the roof of a building overlooking The Manikarnika Ghat in Varanasi on August 23, 2016. India's holy city of Varanasi has been forced to halt cremations along the banks of the sacred river Ganges as deadly floods from monsoon rains hit parts of the country, an official said. More than 100,000 people have been forced from their homes in recent days in northern Uttar Pradesh and neighbouring Bihar states as rain-swollen rivers burst their banks. (Photo by Sanjay Kanojia/AFP Photo)

People walk on the street in Samara, Russia on July 18, 2017. (Photo by David Mdzinarishvili/Reuters)

This computer image provided Monday March 17, 2014 by the Press Office of socialist candidate to Paris Mayor Anne Hidalgo, shows a tunnel of abandoned railway from the 19th century, now ramshackle and overgrown, turned into a cinema. Hidalgo’s plan envisions not just a green space but in the tunnels, places for farming fish and mushrooms. (Photo by AP Photo/Anne Hidalgo's Press Office)

Singer Jason Derulo performs during his Flash Mob with Knicks City Dancers outside of Madison Square Garden on September 28, 2011 in New York City. (Photo by Mike Coppola/Getty Images)