To an outsider, their passion is at times illegal and often on the verge of life and death. But climbing rooftops of high-rise buildings and exploring abandoned facilities is in the blood of these young Muscovites. The small group calls itself “Rudex”, which stands for “roof and decay exploration”, and is akin a Western youth craze known as urbex or “urban exploration” of man-made structures. Here: Urban explorer Vad Him of Rudex team jumps whilst on a rooftop in Moscow, Russia, August 14, 2017. (Photo by Maxim Shemetov/Reuters)

Thailand’s Surasak Waenwiset tries a shot as Hungary’s Marcell Fenyvesi stands nearby, during their Beach Handball Men’s Tournament match in Tecnopolis Park, during the Youth Olympic Summer Games in Buenos Aires, Argentina on October 9, 2018. (Photo by Florian Eisele/AP Photo)

A hot air balloon floats past an almost full rising moon on a warm fall evening near Encinitas, California October 5, 2014. (Photo by Mike Blake/Reuters)

A police officer escorts a civilian away from the scene of a shooting, Sunday, July 22, 2018, in Toronto, Canada. A gunman opened fire in central Toronto on Sunday night, injuring 13 people including a child. Two dead including gunman, police reported. (Photo by Frank Gunn/The Canadian Press via AP Photo)

National Geographic has created “Air, Land & Sea: the 50 greatest wildlife photographs” exhibition. Here: CT4 Crocodile cave on the Salamat river. Set up with Nathan Williamson last chip rain came while we were with the nomads. (Photo by Michael Nichols/National Geographic)

Lisandra Perez, 7, practices in his house before his flute lesson at the Integral System of Artistic Education for Social Inclusion (SIFAIS) center in the poor neighborhood of La Carpio, Costa Rica October 8, 2015. SIFAIS center is developing a social program with the help of 156 volunteers who teach art, music, sports and education, for children and youth living in La Carpio, known for being the home to gangs, violence, drugs and social vulnerability, according to the centre. (Photo by Juan Carlos Ulate/Reuters)

A Maori soldier runs as New Zealand's soldiers march down the Champs Elysees in Paris during a rehearsal of the annual Bastille Day military parade on July 12, 2016. (Photo by Thomas Samson/AFP Photo)

Taking it all in at Trolltunga, a piece of rock which juts horizontally out of a mountain, 700 metres above lake Ringedalsvatnet in Norway. (Photo by Sam Rogers/GuardianWitness)