Jun Sato (2nd L), founder of Japan's first parkour educational institute SENDAI X-TRAIN, demonstrates his parkour skill with other practitionners at a park in Tokyo, Japan November 2, 2016. (Photo by Kim Kyung-Hoon/Reuters)

Damselflies covered in dew rest on a wild flower by the Po River, northern Italy on August 15, 2016. (Photo by Alberto Ghizzi Panizza/Barcroft Images)

Saudi children of al-Fefi family walk up the stairs as they make their way to their schools through Fifa Mountain, in Jazan, south of Saudi Arabia, December 15, 2016. (Photo by Mohamed Al Hwaity/Reuters)

A woman tour skates on the frozen lake of Orlangen, south of Stockholm, Sweden, on December 23, 2016. Tour skating is recreational long distance ice skating on natural ice particularly popular in the Nordic countries. (Photo by Tobias Roestlund/AFP Photo/TT News Agency)

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

Nepalese Hindu women pray to worship Lord Shiva during the first day of the Sarwan Brata festival, the month of fasting, at the premises of Pashupati Temple in Kathmandu, Nepal, 18 July 2016. Thousands of married and single Nepalese Hindu women will gather in temples for each Monday of the Sawan month (spanning from 16 July to 16 August) to pray for a long and prosperous life of their husbands or for a chance to find a good one. (Photo by Narendra Shrestha/EPA)

An artist airbrushes a model during the “World Bodypainting Festival 2017” in Klagenfurt, Austria on July 28, 2017. (Photo by Leonhard Foeger/Reuters)

A girl looks with comic disgust at a guy who falls asleep with a bottle of beer at a party; her friend laughs. (Photo by Edward Corbett/Rex Features/Shutterstock)