Iraqi firefighters try to stop the fire of burning oil wells in Kirkuk, northern Iraq, 02 June 2016. Two Khabbaz oil field wells in Kirkuk Province, northern Iraq, exploded by suspected insurgents, a security official said. (Photo by EPA/Stringer)

Chinese paramilitary guards monitoring passengers as they head to their train to travel to their hometowns for the “Spring Festival” or Lunar New Year at Nantong Railway Station in Jiangsu province, near Shanghai Travellers taking part in the world' s largest annual human migration must be home by January 27 to usher in the new year on January 28. (Photo by AFP Photo/Stringer)

A Palestinian female masked militant from the Al-Quds Brigades, the military wing of the Islamic Jihad, takes part in an Islamic Jihad rally in Rafah, southern Gaza Strip, 29 July 2016. (Photo by Mohammed Saber/EPA)

A student participates in celebrations ahead of the Janmashtami festival, which marks the birth anniversary of Lord Krishna in Mumbai, India, August 23, 2016. (Photo by Danish Siddiqui/Reuters)

Beneath the Swedish capital lies an intricate web of underground train lines. More than 90 of the 100 stations in the 110km tunnel system, sometimes referred to as “the world’s longest art gallery”, have been decorated with paintings, installations, mosaics and sculptures by 150 artists since the 1950s. After spending a couple of weeks exploring arctic Norway and Sweden, London-based travel photographer Conor MacNeill headed underground to capture images of the metro stations. Here: A rainbow arcs over a girl on the platform of Stadion station. (Photo by Conor MacNeill/The Observer)

View of a damaged bridge at the Iguacu Falls on June 12, 2014, in Foz do Iguacu, Brazil, following the overflowing of the Parana river. In neighbouring Paraguay flooding has forced the evacuation of about 150,000 people in Paraguay's capital city Asuncion, authorities said. (Photo by Norberto Duarte/AFP Photo)

A bride stretches before the event during the “Running of the Brides” race, in Bangkok, Thailand, December 2, 2017. Six hundred of to be brides and their grooms compete a run race aimed to win more than two million baht (61,000 US dollars or 51,000 euro) of wedding package prizes including a pair of white gold diamond rings and honeymoon trip to the Maldives. (Photo by Athit Perawongmetha/Reuters)

A man stands next to the body of a migrant child washed up on a beach in Canakkale's Bademli district on January 30, 2016 after at least 37 migrants drowned when their boat sank in the Aegean Sea while trying to cross from Turkey to Greece, Turkey's state-run Anatolia news agency reported. The migrants, who included those from Myanmar, Afghanistan and Syria, set sail from the Canakkale province to reach the nearby Greek island of Lesbos, Anatolia said. (Photo by Ozan Kose/AFP Photo)