An Israeli army officer gives explanations to journalists during an army organised tour in a tunnel said to be used by Palestinian militants for cross-border attacks, July 25, 2014. (Photo by Jack Guez/Reuters)

Tommy Lindsey holds an enormous maple leaf that he found in Mount Vernon, Wash., October 28, 2013. Lindsey was walking with his family when he picked up the leaf that is more than two feet from stem to tip and more than 21 inches wide. (Photo by Frank Varga/The Skagit Valley Herald)

Performers line up during the closing ceremony of the 2014 Winter Olympics, Sunday, February 23, 2014, in Sochi, Russia. (Photo by Darron Cummings/AP Photo)

Members of the Dominican Armed Forces participate in a commemorative act on the 170th anniversary of national independence at the esplanade of Santo Domingo, on February 27, 2014. (Photo by Orlando Barria/EPA)

Chinese hostesses, who serve the delegates of the Chinese People's Political Consultative Conference and National People's Congress, have souvenir photos taken in front of the Great Hall of the People during sessions of the CPPCC and NPC held in Beijing, China Tuesday, March 4, 2014. (Photo by Andy Wong/AP Photo)

Amundsen-Scott South Pole Station experiences months of darkness. The sun dips below the horizon on March 21, after which follows several weeks of twilight before complete darkness results. Photo taken on June 25, 2009. (National Science Foundation/Jeremy Johnson)

A man carries a smoke flare as far-right activists march during the Gay Pride parade on June 12, 2016 in Kiev. More than 700 gay rights activists marched through central Kiev on June 12 amid a massive police presence for the third such gay pride event in the ex-Soviet country where homophobia remains widespread. The June 12 march was the first ever gay pride rally to be held in central Kiev, prompting an unprecedented security operation with several thousand police and National Guard officers lining the route during the event, which lasted around 20 minutes. (Photo by Yuriy Kirnichny/AFP Photo)

Muslims offer prayers during Jumat-ul-Vida or the last Friday of the holy fasting month of Ramadan in Allahabad, India, July 1, 2016. Muslims throughout the world are marking the month of Ramadan, the holiest month on the Islamic calendar, by fasting from dawn till dusk. (Photo by Jitendra Prakash/Reuters)