Children playing on Walled City rooftop in Hong Kong, 1989. The lack of formal governance in the Walled City led to challenges, but it also fostered a unique system of informal social order. (Photo by Greg Girard/The Guardian)

A student protester throws a stone against a riot police vehicle during a demonstration to demand changes in the education system in Santiago, Chile, April 21, 2016. (Photo by Ivan Alvarado/Reuters)

The possible surface of TRAPPIST-1f, one of seven newly discovered planets in the TRAPPIST-1 system that scientists using the Spitzer Space Telescope and ground based telescopes have discovered. (Photo by Reuters/NASA/JPL-Caltech)

Wounded people walk after clashes with riot police in central Kiev February 18, 2014. Ukrainian riot police advanced on the heart of 12-week-old protests against President Viktor Yanukovich on Tuesday and security forces set a deadline to end disturbances after at least five protesters were reported killed in a day of clashes. (Photo by Vlad Sode/Reuters)

Fighters of the Free Syrian Army fire an anti-aircraft weapon in the rebel-held Mashhad area in southeastern Aleppo, on December 12, 2016, as they battle Syrian government forces during an operation to retake the embattled city. The crucial battle for Aleppo entered its “final phase” after Syrian rebels retreated into a small pocket of their former bastion in the face of new army advances. The retreat leaves opposition fighters confined to just a handful of neighbourhoods in southeast Aleppo, the largest of them Sukkari and Mashhad. (Photo by AFP Photo/Stringer)

This photo released by the Cleveland Animal Protective League shows Lurleen, the nursing mother and Noland the puppy snuggling up Wednesday, June 19, 2013, in Cleveland. Lurleen already is caring for four newborn kittens and now is nursing the orphaned week-old pit bull puppy in Cleveland. (Photo by AP Photo/Cleveland Animal Protective League)

A Common seal named Groot is prepared for release in a transfer cage at Seal Rescue Ireland wildlife sanctuary where two rescued and rehabilitated seals are released back into the sea after months of care in Wexford, Ireland, June 12, 2016. (Photo by Clodagh Kilcoyne/Reuters)

A spooky sight to behold! This is what a psychiatric hospital that has been abandoned for years looks like. Complete with bowling alley and a theater, the hospital shows just how much nature has weathered it over time as paint peels from the walls and the mattress gather dust. Here: This area of the hospital was last used as a day care center in the early 2000s. (Photo by Will Ellis/Caters News)