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)

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)

Artist German Vinogradov acts in the performance of the burning of installation, devoted to Maslenitsa, or Pancake Week, a pagan holiday marking the end of winter, in the village of Nikola-Lenivets, Kaluga region, Russia, February 17, 2018. (Photo by Maxim Shemetov/Reuters)

A model presents a creation by designer Maxime Simoens as part of his Haute Couture Fall-Winter 2018/2019 fashion show for fashion house Azzaro Couture in Paris, France, July 1, 2018. (Photo by Regis Duvignau/Reuters)

Russian servicemen look on as a Mi-24 helicopter fly overhead during the Open Water competition for pontoon bridge units, as part of the International Army Games 2018, outside Murom, Russia August 3, 2018. (Photo by Maxim Shemetov/Reuters)

Audrey Lu and Misha Mitrofanov of the United States compete in the Pairs Short Program during day 1 of the ISU Grand Prix of Figure Skating Rostelecom Cup at Megasport Arena on November 15, 2019 in Moscow, Russia. (Photo by Maxim Shemetov/Reuters)

A Russian Su-35S combat aircraft and a Tu-95ms strategic bomber fly in formation above a church during a rehearsal for the flypast, which is part of a military parade marking the anniversary of the victory over Nazi Germany in World War Two, in Moscow, Russia on May 4, 2022. (Photo by Maxim Shemetov/Reuters)

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)