Members of Libyan forces allied with the UN-backed government fire a weapon towards Islamic State militants in neighbourhood Number One in central Sirte, Libya August 28, 2016. (Photo by Ismail Zitouny/Reuters)

A man stands at a passenger train damaged in a collision with a freight train in Moscow region May 20, 2014. The passenger train on its way to Moldova collided with a freight train near Moscow on Tuesday, killing at least four people and injuring 15, a spokeswoman for Russia's Emergencies Ministry said. The reason for the collision, near the town of Naro-Fominsk 55 km (34 miles) southwest of Moscow, was not immediately clear. (Photo by Grigory Dukor/Reuters)

A Brazil fan waits for the start of the group A World Cup soccer match between Brazil and Croatia, the opening game of the tournament, in the Itaquerao Stadium in Sao Paulo, Brazil, Thursday, June 12, 2014. (Photo by Felipe Dana/AP Photo)

Runners cross the Verrazano-Narrows Bridge shortly after the start of the New York City Marathon in New York, November 2, 2014. (Photo by Lucas Jackson/Reuters)

An Iranian man sells colorful ropes at the Tehrans old Bazaar, the place where the main economy trades take place, in Tehran, Iran, 25 January 2016. Reports state that Iranian officials expected the Iranian economy to grow on an average of eight percent over the coming five years following the lifting of sanctions against Iran. (Photo by Abedin Taherkenareh/EPA)

A student uses a ruler to measure the distance between forks before a formal dinner at The International Butler Academy China on September 16, 2014 in Chengdu, China. Over the last several years, there has been a surge in demand among China's wealthy for Western-trained butlers, with many academies seeing large portions of their graduating classes hired by Chinese families or companies. (Photo by Taylor Weidman/Getty Images)

Protesters sit in a cafe during a “SlutWalk” protest, in which several hundred participants march through the centre of Jerusalem, May 13, 2016. The SlutWalk movement began after a Toronto policeman suggested in 2011 that women could avoid sexual assault by not dressing like a “sl*t”. (Photo by Amir Cohen/Reuters)

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)