Engine driver Josef Kowatsch (top L) steers a train through the NEAT Gotthard Base Tunnel during a media visit near the town of Erstfeld August 24, 2015. Crossing the Alps, the world's longest train tunnel should become operational at the end of 2016, consisting of two parallel single track tunnels, each of a length of 57 km (35 miles). (Photo by Arnd Wiegmann/Reuters)

A woman with a Japanese style full back body tattoo at the 12th London International Tattoo Convention, which opened today in Tobacco Dock, east London on September 23, 2016. The show features over 400 of the world's finest, most prestigious and elite tattoo artists as well as a showcasing alternative culture in the form of piercing, burlesque and the Miss Pin Up UK competition. Around 20,000 people will attend over the weekend. (Photo by Michael Preston/Alamy Live News)

Cloud inversion taken at Sunrise in Mam Tor, Derbyshire, UK on August 30, 2016. (Photo by David Zdanowicz/Rex Features/Shutterstock)

A Pakistani devotee dances to celebrate the three-day annual festival to pay tribute to the famous saint Al-Sheikh Ali Bin Usman Al-Hajveri known as Data Ganjbaksh at outside his shrine in Lahore, Pakistan, Sunday, November 20, 2016. Thousands of people traveled from all over Pakistan to attend the celebrations. (Photo by K.M. Chaudary/AP Photo)

VIETNAM: A Vietnamese woman, wearing the traditional “ao dai” long dress, poses for photos along peach blossom flowers ahead of the Vietnamese “Tet” (Lunar New Year festival), in a field in Hanoi, Vietnam, February 2, 2016. (Photo by Reuters/Kham)

People in Mexico wave at U.S. Border Patrol agents on horseback patrolling the U.S.-Mexico border fence near San Diego, California, U.S., November 10, 2016. (Photo by Mike Blake/Reuters)

A woman reacts as anti-government protesters place a dead body on a stretcher after violence erupted in the Independence Square in Kiev, in this February 20, 2014 file photo. (Photo by Vasily Fedosenko/Reuters)

Children displaced as a result of Boko Haram attacks in the northeast region of Nigeria, run at a camp for internally displaced persons (IDP) in Yola, Adamawa State January 13, 2015. Boko Haram says it is building an Islamic state that will revive the glory days of northern Nigeria's medieval Muslim empires, but for those in its territory life is a litany of killings, kidnappings, hunger and economic collapse. (Photo by Afolabi Sotunde/Reuters)