Tribesmen loyal to the Houthi movement perform the Baraa dance during a gathering to show support to the movement in Sanaa, Yemen, May 19, 2016. Bara or Baraa dance is one of the several traditional outdoor dances performed by men in the country of Yemen. Bara dance literally means a dagger dance, where each dancer holds a dagger. The style of the Bara dance differs from tribe to tribe. It is performed on special occasions. (Photo by Khaled Abdullah/Reuters)

Up to 35% of Mongolians still live a nomadic life, depending on their land to survive. But environmental changes, particularly desertification, means this way of life is under threat. Korean photographer Daesung Lee’s Futuristic Archaeology images show billboard-size backdrops of lush steppe contrasting with actual scenery as former nomads enact scenes of hunting, herding and Mongolian wrestling. (Photo by Daesung Lee)

People watch as lava flows from an eruption of a volcano on the Reykjanes Peninsula in southwestern Iceland late on Monday, March 29, 2021. Iceland's latest volcano eruption is still attracting crowds of people hoping to get close to the gentle lava flows. The eruption in Geldingadalur, near Iceland's capital Reykjavik, is not seen as a threat to nearby towns and the slow flows mean people can get close to action without too much harm. (Photo by Marco Di Marco/AP Photo)

Revellers hit the town on Saturday, February 19, 2022 for a pub crawl despite the snow in Leeds, United Kingdom. The UK capital was placed under its first ever “red” weather warning, meaning there is “danger to life”. The same level of alert was in place across southern England and South Wales, where schools were closed and transport paralysed. (Photo by Nb press ltd)

A woman dressed up for Halloween travels on a Metro train in São Paulo, Brazil on October 30, 2017. (Photo by Cris Faga/Rex Features/Shutterstock)

Passengers travel in an overcrowded train in the eastern Indian city of Patna, February 23, 2010. (Photo by Krishna Murari Kishan/Reuters)

A subway worker walks away after a train departed the station in central Pyongyang, North Korea May 7, 2016. (Photo by Damir Sagolj/Reuters)

A child attends a training session in a swimming pool on July 10, 2007 in Wuhan of Hubei Province, China. (Photo by China Photos/Getty Images)