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)

The sanctuary of Lourdes flooded, in Lourdes, southwestern France, Tuesday, June 18, 2013. French rescue services and police are evacuating hundreds of pilgrims from hotels threatened by floodwaters from a rain-swollen river in the Roman Catholic shrine town of Lourdes. (Photo by Bob Edme/AP Photo)

This Monday, September 15, 2014 photo shows glazed bricks displayed at the Iraqi National Museum in Baghdad. The Islamic State militants seek to purge society of all influences that don't conform with their strict, puritanical version of Islam. That means destroying not only relics seen as pagan but also Muslim sites they see as contradicting their ideology, particularly Sunni Muslim shrines they see as idolatrous as well as mosques used by Shiites, a branch of Islam they consider heretical. (Photo by Hadi Mizban/AP Photo)

A pro-Russian armed man secures crash site wreckage of the Malaysia Airlines Boeing 777 plane (flight MH17) at the site of the plane crash near the settlement of Grabovo in the Donetsk region November 16, 2014. Local emergency services have begun collecting parts of the wreckage from its crash site in the middle of the conflict zone, Dutch air accident investigators said on Sunday. Dutch inspectors had hoped to collect the parts themselves, following the downing of the flight on July 17 that killed 298 people, two thirds of them Dutch citizens. But they remain concerned about the safety of their staff in the rebel-held conflict zone, and so have decided to work with local services following an initial focus on finding human remains and belongings. (Photo by Antonio Bronic/Reuters)

A participant shows off a belt buckle during the 20th annual Seattle Invitationals, an amateur Elvis impersonator competition, in Seattle, Washington January 23, 2015. The event drew hundreds of spectators for 20 contestants at the Crocodile, a venue in Seattle's Belltown neighborhood. (Photo by David Ryder/Reuters)

The cruise ship Costa Concordia lies stricken off the shore of the island of Giglio, on January 17, 2012 in Giglio Porto, Italy. More than four thousand people were on board when the ship hit a rock off the Tuscan coast. At least 11 people have been confirmed dead and another 24 missing. (Photo by Laura Lezza/Getty Images)

Thai classical dancers perform for Phra Phrom, the Thai interpretation of the Hindu god Brahma, at the Erawan Shrine in Bangkok, Thailand, Friday, September 4, 2015. Thai authorities unveiled the restored centerpiece Friday of the Erawan Shrine, in the latest bid to restore confidence among Bangkok's tourism and business communities almost three weeks after a deadly bombing. (Photo by Sakchai Lalit/AP Photo)

Dr. Hannah Cobb from The University of Manchester looks at a viking sword during a viewing at CFA Archaeology of artefacts discovered from the first fully intact Viking boat burial site on October 18, 2011 in Edinburgh, Scotland. (Photo by Jeff J Mitchell/Getty Images)