Participants compete in the Mud Day Race extreme run competition at El Goloso military base, outside Madrid, Spain, June 11, 2016. Thousands of athletes got covered in mud as they celebrated International Mud Day running a 13-kilometer obstacle course on a sunny Saturday with heatwave-like temperatures up to a 29 degrees Celcius (around 84 degrees Fahrenheit). (Photo by Juan Medina/Reuters)

Participants of the Sarenza High Heel Race 2015 warm up prior to the race during a party of the online shoe store, in Paris, Thursday, October 15, 2015. Competitors in teams of three girls race wearing shoes with more than 8 cm-high heels. (Photo by Francois Mori/AP Photo)

The Al-Gaffal is an annual long-distance race between crews sailing 60-ft. traditional wooden boats called dhows and takes place in the Persian Gulf, between the island of Sir Bu Nair, near the Iranian coast and the Gulf emirate of Dubai. Photo: Traditional wooden boats, or dhows, compete at sunrise during the Al Gaffal race, a long-distance dhow sailing race, near Sir Bu Nuayr, near Sharjah May 18, 2014. (Photo by Martin Dokoupil/Reuters)

Doctor Boaz Zissu of the Bar Ilan University shows the inscription on a 2,000-year-old ossuary at the Rockefeller Museum on June 30, 2011 in Jerusalem, Israel. The Israel Antiquities Authority have confirmed the credibility of the ancient ossuary, otherwise known as a stone chest in which to store bones, as bearing the name of a relative of the high priest Caiaphas from the New Testament. Laboratory tests have come back saying that the inscription with the name of “Miriam daughter of Yeshua son of Caiaphas, priest of Maaziah from Beth Imri” is both “genuine and ancient”. (Photo by Uriel Sinai/Getty Images)

A follower shows a ring of La Santa Muerte (The Saint of Death), a cult figure often depicted as a skeletal grim reaper, near at the saint's altar at Tepito neighborhood, in Mexico City January 1, 2015. Followers gather at the saint's altar at the start of the new year to leave offerings of apples, flowers, cigarettes, coloured candles and tequila to thank the saint for favours that have been granted and to ask for new ones in the new year. (Photo by Edgard Garrido/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)

Pigs race around the track at the Pig Racing and Diving display at the Sydney Royal Easter Show on April 10, 2009 in Sydney, Australia. (Photo by Mark Kolbe/Getty Images)

People attend the Stranavigli Water Race held at the Naviglio Grande on July 16, 2011 in Milan, Italy. Stranavigli Water Race is an annual creative contest on the water. (Photo by Vittorio Zunino Celotto/Getty Images)