A girl plays in a water-jets fountain in Moscow, Russia, 23 June 2021. The temperature exceeded 36 degrees Celsius in Moscow. The weather in Moscow broke the temperature record high of the day, held since 1948, when meteorologists recorded +33.6. (Photo by Sergei Ilnitsky/EPA/EFE)

Indian girls apply colored powder on each other as they wear protective masks as a precautionary measure against coronavirus, during Holi festival celebrations in Bhopal, India, 26 March 2021. Holi marks the beginning of the spring season. Holi will be celebrated as the Hindu spring festival of colors across the country on 29 March. (Photo by Sanjeev Gupta/EPA/EFE)

Calves look out as they are transported in a cart in the village of Litkovka, in Omsk region, Russia on March 20, 2021. (Photo by Alexey Malgavko/Reuters)

Commuters hang off a local passenger train in the morning in Colombo, Sri Lanka September 8, 2016. (Photo by Dinuka Liyanawatte/Reuters)

A coach wipes away tears and comforts a girl who was feeling tired during gymnastics lessons at the Shanghai Yangpu Youth Amateur Athletic School in Shanghai, China, May 4, 2016. (Photo by Aly Song/Reuters)

Participants dance and climb on an art installation as approximately 70,000 people from all over the world gather for the 30th annual Burning Man arts and music festival in the Black Rock Desert of Nevada, U.S. August 31, 2016. (Photo by Jim Urquhart/Reuters)

Couple getting intimate on couch. (Photo by Vincent Besnault/Getty Images)

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)