Mrs. Marie Graskamp of Milwaukee shows the different positions one might assume when entering the bomb shelter in Milwaukee September 3, 1958. This circular entrance is about three feet in diameter. This is the entrance (according to the builders) that would connect to the cellar of a home assuming the shelter was in the ground for added protection. If a bombing should occur, all members of family would proceed to the cellar and then through the circular port into the shelter. (Photo by AP Photo)

Stray dogs stand on tombs in Diamond Hill cemetery in Hong Kong, China, 04 April 2017. According to the lunar calendar, the Qingming Festival is observed on 04 April . The Qingming Festival, also known as Tomb-Sweeping Day, is marked by Chinese people by going to the cemetery to cleaning up tombs, bring flowers, and making offerings to their ancestors. (Photo by Jerome Favre/EPA)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

DJ Evans Mireku Kissi (R) and fashion stylist Daniel Quist ride a motorcycle in front of a street side bar in Accra, Ghana. June 10, 2015. Young artists in Ghana's capital have evolved a new style that is turning heads and challenging accepted notions of African fashion. (Photo by Francis Kokoroko/Reuters)

An orangutan named “Pacquiao” dressed in a Santa Claus costume reacts as he joins an “Animal Christmas Party” at the Malabon zoo in suburban Malabon, north of Manila, Philippines Monday, December 21, 2015. The Malabon Zoo is one of the largest private collections of exotic and endemic animals in the Philippines. (Photo by Aaron Favila/AP Photo)

A wolf looks into the camera at the 30 km (19 miles) exclusion zone around the Chernobyl nuclear reactor in the abandoned village of Orevichi, Belarus, March 2, 2016. What happens to the environment when humans disappear? Thirty years after the Chernobyl nuclear disaster, booming populations of wolf, elk and other wildlife in the vast contaminated zone in Belarus and Ukraine provide a clue. (Photo by Vasily Fedosenko/Reuters)

The disused bobsled track from the Sarajevo 1984 Winter Olympics is seen on Mount Trebevic, near Sarajevo, September 19, 2013. Abandoned and left to crumble into oblivion, most of the 1984 Winter Olympic venues in Bosnia's capital Sarajevo have been reduced to rubble by neglect as much as the 1990s conflict that tore apart the former Yugoslavia. (Photo by Dado Ruvic/Reuters)

In this photograph taken on August 25, 2016, an Afghan shepherd watches over his sheep as they graze on the outskirts of Herat. (Photo by Aref Karimi/AFP Photo)