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)

A pilot inflates a hot air balloon while taking part in the 38th International Balloon Festival of Chateau-d'oex, Switzerland, 23 January 2016. The festival takes place from 23 to 31 January. (Photo by Vincent Vannay/EPA)

The giant metal structure sits 330ft above the ground on the roof of a 22 storey office block in Dutch capital Amsterdam on September 6, 2016. Tourists sit in a playground-style chair as they propel themselves them over the edge of the building with only thin-air between them and the ground below. Engineers spent several years designing and building the breathtaking swing. By being fixed to the top of a building it reaches new heights – dwarfing other swings around Europe but trailing behind the 1,150ft high mechanical rides at the Stratosphere Hotel in Las Vegas, Nevada. (Photo by Huub Zeeman/SWNS.com)

A veterinarian kisses an 8-month-old cat, wearing a prosthetic two-wheel device, at a veterinary hospital in Chongqing municipality, March 16, 2015. The cat's rear legs lost the abilty to walk after falling from the ninth to fifth floor of a building last November, its since undergone four major surgeries which included removing parts of its organs, local media reported. (Photo by Reuters/China Daily)

Belgian yoga teacher Dorien Dierckx, 29 from Brussels enjoys a beer while relaxing in a jacuzzi full of hot water and a mixture of ingredients used to make beer, and where customers can serve their own beer from the tap at the Good Beer Spa in Brussels, Belgium on May 12, 2021. (Photo by Yves Herman/Reuters)

A participant flies a kite during the “Letatlin N4” annual Festival of Kites, in Moscow, Russia on June 6, 2021. (Photo by Dimitar Dilkoff/AFP Photo)

Fans attend “The Batman” special screening at BFI IMAX Waterloo on February 23, 2022 in London, England. (Photo by Jeff Spicer/Getty Images for Warner Bros.)

Drone view of vehicles after part of the ceiling collapsed in a mall in Osasco, Brazil on March 9, 2023. (Photo by Carla Carniel/Reuters)