Members of Brazil's Movimento dos Sem-Teto (Roofless Movement) stand in the hallway of one of the 11 empty buildings that the movement took over recently, in the centre of Sao Paulo, November 6, 2012. According to City Hall, there are some 400,000 people in need of stable housing, including the 4,000 families of the Roofless Movement who are squatting in abandoned or vacant buildings that range from apartment blocks to hotels, in Sao Paulo, the largest city in South America. (Photo by Nacho Doce/Reuters)

A gibbon drinks from a soft drink bottle, given by a tourist, at a zoo in Kunming, Yunnan province, June 18, 2015. (Photo by Wong Campion/Reuters)

Last weekend, the National Building Museum in Washington, D.C., opened a 10,000 square-foot ball pit to the general public, and everyone cheered that, finally, someone made their childhood dreams come true.

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)

“Entwined Lives”. Tim Laman, US Winner, Wildlife photographer of the year. A young male orangutan makes the 30-metre climb up the thickest root of the strangler fig high above the canopy in Gunung Palung national park, one of the few protected orangutan strongholds in Indonesian Borneo. Laman had to do three days of climbing to position several GoPro cameras that he could trigger remotely. This shot was the one he had long visualised, looking down on the orangutan within its forest home. (Photo by Tim Laman/2016 Wildlife Photographer of the Year)

A Pegasus airplane is seen stuck in mud as it skidded off the runway after landing in Trabzon Airport, Turkey early Sunday on January 14, 2018. A passage plane which belongs to Turkey's Pegasus Airlines skidded off the runway of Trabzon airport Saturday and ended up halfway down a steep slope into the Black Sea, Turkish media reported on Sunday. 162 passengers and crew on board were safely evacuated. (Photo by Hakan Burak Altunoz/Anadolu Agency/Getty Images)

A hungry cow smiles for the camera in Salzburg, Austria. One of a series of funny animal mugshots taken by Chanel Cartell and Stevo Dirnberger during their travels around the globe. (Photo by Chanel Cartell/Stevo Dirnberger/Rex Features/Shutterstock)

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)