Siberian Huskies pull a contestant during the “Kara-Dag 2016” open amateur dog sled and skijoring race near the village of Yelovoye in Taiga district, outside Krasnoyarsk, Siberia, Russia, February 21, 2016. Dogs and their owners from various regions of Siberia took part in an annual race. (Photo by Ilya Naymushin/Reuters)

A white Bengal tiger cub plays with its mother in a zoo in the Siberian city of Novosibirsk, about 2,800 kilometers (1,750 miles) east of Moscow, Russia, Tuesday, April 21, 2015. Two blue-eyed Bengal tiger cubs were born in March to a couple of white tigers at Novosibirsk zoo. (Photo by Ilnar Salakhiev/AP Photo)

Painted glass Christmas and New Year decorations are pictured at the “Yolochka” (Christmas tree) factory, which has been producing glass decorations and toys for the festive season since 1848, in the town of Klin outside Moscow, Russia, November 24, 2016. (Photo by Maxim Zmeyev/Reuters)

Members of the Honour Guard and the central military band of the Mongolian armed forces perform during the International Military Music Festival “Spasskaya Tower” media preview in Red Square in Moscow, Russia, August 26, 2016. (Photo by Sergei Karpukhin/Reuters)

In this handout image provided by Red Bull, Artem Silchenko of Russia dives from the 27 metre platform at training on Hong Island in the Andaman Sea during the final stop of the 2013 Red Bull Cliff Diving World Series on October 25, 2013 at Krabi, Thailand. (Photo by Romina Amato/Red Bull via Getty Images)

Artist German Vinogradov acts in the performance of the burning of Maslenitsa tower, devoted to Pancake Week, a pagan holiday marking the end of winter, in the village of Nikola-Lenivets, Kaluga region, Russia, February 25, 2017. (Photo by Maxim Shemetov/Reuters)

Paramedics carry an injured woman out from a subway station after a rush-hour subway train derailment, to be transported by a medical helicopter in Moscow, Russia, on Tuesday, July 15, 2014. A rush-hour subway train derailed in Moscow Tuesday, killing 20 people and injuring at least 150, emergency officials said. Several cars left the track in the tunnel after a power surge triggered an alarm, which caused the train to stop abruptly. (Photo by Ivan Sekretarev/AP Photo)

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)