Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)

In this photograph taken on June 28, 2015, a hiker in Hong Kong takes a picture of the city from a walking trail. The southern Chinese territory is crisscrossed by more than 180 miles of designated hiking trails. (Photo by Alex Ogle/AFP Photo)

Olaf Niess catches swans on the river Alster near the town hall in Hamburg, Germany, 17 November 2015. The Alster swans are moving to their ice-free winter quarters on the Eppendorf Muehlenteich millpond until spring. (Photo by Bodo Marks/EPA)

Jockeys spur buffalos during the Makepung buffalo races at Jembrana in Bali, Indonesia on October 23, 2016. Makepung is a tradition for farmers to celebrate a bumper harvest in Bali. (Photo by Kadek Raharja/Xinhua/Barcroft Images)

A man takes photo of his colleague with a mobile phone on the burning oil tanker at the ship-breaking yard in Gaddani, Pakistan, November 2, 2016. Reports state that at least eighteen workers were killed and more than 100 were wounded in a blast at Gaddani ship breaking yard near Karachi on 01 November. Initial reports suggest the blast occurred when a gas cylinder exploded inside an oil tanker being broken up for scrap. (Photo by Akhtar Soomro/Reuters)

Performers from the Joles ethnic group in Gambia prepare to perform with sharp blades which they say will demonstrate the magic powers of a spiritual water, that will make them immune to the cuts, during a campaign rally by incumbent President Yahya Jammeh, leader of the APRC (The Alliance for Patriotic Reorientation and Construction) in Bikama on November 24, 2016. As electoral favorite Jammeh seeks his fifth term in power, a two-week campaign period will come to an end next week ahead of the December 1st presidential election with political leaders canvassing in rural areas. (Photo by Marco Longari/AFP Photo)

Villagers look on as Mount Sinabung volcano spews thick volcanic ash, as seen from Beganding village in Karo, North Sumatra province, on May 19, 2017. Sinabung roared back to life in 2010 for the first time in 400 years. After another period of inactivity, it erupted once more in 2013 and has remained highly active since. (Photo by Ivan Damanik/AFP Photo)

A wounded Syrian girl looks on at a make shift hospital in the rebel-held area of Douma, east of the capital Damascus, following shelling and air raids by Syrian government forces on August 22, 2015. At least 20 civilians and wounded or trapped 200 in Douma, a monitoring group said, just six days after regime air strikes killed more than 100 people and sparked international condemnation of one of the bloodiest government attacks in Syria's war. (Photo by Abd Doumany/AFP Photo)