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)

International film actress Gillian Anderson pictured on the rooftop of the Ritz-Carlton Hotel overlooking Red Square in a British Airways Business Class seat to launch the British Airways long haul service on the London – Moscow route on March 6, 2012 in Moscow, Russia. (Photo by Gareth Cattermole/Getty Images For British Airways)

Reveller Jacqueline Fernandez looks on in the rain during the 26th Annual Kensington Market Winter Solstice Parade in Toronto, Canada, December 21, 2015. (Photo by Mark Blinch/Reuters)

A sign reading “STOP Danger of Avalanches” blocks a local road on January 11, 2012 near Ischgl, Austria. Over the last few days heavy snowfalls have caused chaos in parts of Austria and Switzerland by blocking rail and road connections, stranding vacationers at mountain ski resorts and creating the risk of avalanches throughout the region. (Photo by Johannes Simon/Getty Images)

Performers line up during the closing ceremony of the 2014 Winter Olympics, Sunday, February 23, 2014, in Sochi, Russia. (Photo by Darron Cummings/AP Photo)

Julia Zlobina and Alexei Sitnikov of Azerbaijan gesture as they wait in the results area after competing in the ice dance free dance figure skating finals at the Iceberg Skating Palace during the 2014 Winter Olympics, Monday, February 17, 2014, in Sochi, Russia. (Photo by Vadim Ghirda/AP Photo)

A model walks the runway during the Craig Lawrence show at London Fashion Week Autumn/Winter 2012 at Somerset House on February 19, 2012 in London, England. (Photo by Stuart Wilson/Getty Images)

A model walks down the runway during the Safilo fashion show at the Mercedes-Benz Fashion Pavilion on January 30, 2012 in Stockholm, Sweden. (Photo by Ian Gavan/Getty Images)