A boy sits in a canoe in front of a shed built on a raft in the Makoko fishing community on the Lagos Lagoon, Nigeria February 29, 2016. In Makoko, a sprawling slum of Nigeria's megacity Lagos, a floating school capable of holding up to a hundred pupils has since November brought free education to the waterways known as the Venice of Lagos. It offers the chance of social mobility for youngsters who, like most of the city's 21 million inhabitants, lack a reliable electricity and water supply and whose water-based way of life is threatened by climate change as well as rapid urbanisation. (Photo by Akintunde Akinleye/Reuters)

A man looks at a mural painted on the walls of houses in Zaraeeb, created by French-Tunisian artist El Seed, in the shanty area known also as Zabaleen or “Garbage City” on the Mokattam Hills in eastern Cairo, Egypt, April 4, 2016. (Photo by Amr Abdallah Dalsh/Reuters)

A member of the Diablada Urus group attends the carnival parade in Oruro, Bolivia February 25, 2017. (Photo by David Mercado/Reuters)

A man walks on a bridge crossing over the Besor stream on a rainy day, near Kibbutz Tze'elim in Israel's southern Negev desert February 16, 2017. (Photo by Amir Cohen/Reuters)

A man sits waiting for a train on the London Underground in 1890, when the platform floors were still made from wooden floorboards. (Photo by Hi-Story/Alamy Stock Photo)

In a July 14, 1967 file photo, left, National Guardsmen make their way along Market Street in Newark, N.J, after an evening of deadly rioting and looting in what came to be known as the Newark riots. In a June 16, 2017 photo, right, an ambulance drives on the same block 50 years later. (Photo by AP Photo/File, left; Julio Cortez, right)

The Mile O' Mud is a 7/8-mile oval track with a 1/8-mile diagonal lane slashed through the center. The racing lanes are approximately 60 feet wide. On average, the muddy water is four to six feet deep, with three strategically placed holes. The largest hole, located in front of the grandstand, is the treacherous “Sippy Hole”, named for the legendary driver “Mississippi” Milton Morris, Swamp Buggy King 1955, who repeatedly got stuck in it. (Photo by Malcolm Lightner)

Unidentified relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo react as they wait outside the Egyptair in-flight service building where relatives are being held at Cairo International Airport, Egypt May 19, 2016. (Photo by Amr Abdallah Dalsh/Reuters)