A citizen rides in smog on December 20, 2016 in Jinan, Shandong Province of China. Air quality index (AQI) readings exceeded 400 and some schools have suspended classes in Jinan. (Photo by VCG/VCG via Getty Images)

Girls watch a procession during the “Fiesta de las Palancas” celebration to ask for blessings and abundance during the new year in Panchimalco, El Salvador, January 5, 2017. (Photo by Jose Cabezas/Reuters)

Indian passengers travel on a local train in New Delhi, India, October 2017. Constructed in 1975 to bypass the crowded and passenger-heavy Old Delhi, New Delhi and Hazrat Nizamuddin railway stations, the railway line once used to be the lifeline of the capital. (Photo by Ankur Dutta/Barcroft Media)

Urban photographer Roman Robroek spent five years scouring the continent for the grandest examples of forgotten architectural beauty. Here: Watch your step on this Polish spiral staircase. (Photo by Roman Robroek/South West News Service)

Girls bath inside a drum on a hot summer day at a field in New Delhi, April 18, 2017. (Photo by Adnan Abidi/Reuters)

Cosplay fans attend the Animation Comic Games (ACG) Culture Festival in Xi'an, capital of northwest China's Shaanxi Province, May 28, 2017. The festival kicked off on Saturday, attracting lots of cosplay fans. (Photo by Liu Xiao/Xinhua)

This photo of an elephant seal and Gentoo penguin shot by Andrew James in Yankee Harbour, Antarctica. (Photo by Andrew James/Travel Photographer of the Year)

Young U.S. visitors pose for a photograph next to a vintage car in Havana March 16, 2016. (Photo by Ueslei Marcelino/Reuters)