This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

Actress Anna Valle attends the Roberto Cavalli Autumn/Winter 2012/2013 fashion show as part of Milan Womenswear Fashion Week on February 27, 2012 in Milan, Italy. (Photo by Vittorio Zunino Celotto/Getty Images)

People look at a Christmas tree decorated with colourful lights at a residential compound in Beijing on December 8, 2017. (Photo by Nicolas Asfouri/AFP Photo)

A person stands near the “Untitled” installation of miniature elevators by Maurizio Cattelan at a preview of the Postwar and Contemporary Art Evening Sale at Christie's auction house on November 4, 2011 in New York City. The 33-inch functioning elevator installation is expected to realize $400,000-$600,000 at the November 8 auction. (Photo by Mario Tama/Getty Images)

Daniel Filip, Tech Lead Manager for Google Maps, carries the Trekker, a 15-camera device, while mapping the Inca citadel of Machu Picchu for Google Street View in Cuzco, Peru, August 11, 2015. (Photo by Pilar Olivares/Reuters)

A model presents a creation from the fashion label Kakopieros during Australian Fashion week in Sydney, Australia, May 20, 2016. (Photo by David Gray/Reuters)

People stand with sheep for sacrifice outside a church during St. George's Day celebration in the village of Ikalto, Georgia, November 23, 2015. Georgia marks on Monday one of its most popular religious and public holidays. (Photo by David Mdzinarishvili/Reuters)