Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

“Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth”. – Oscar Wilde. (Photo by Lala Roe)

Soccer is played on a television mounted in a workshop in the Willets Point area of Queens in New York October 27, 2015. Willets Point, also known as the Iron Triangle, is an industrial precinct that sits in the shadow of Citi Field, home of the New York Mets baseball team. Many businesses within Willets Point employ a largely immigrant workforce. (Photo by Andrew Kelly/Reuters)

Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

Masks of Republican presidential candidate Donald Trump (C) and Joaquin "El Chapo" Guzman (2nd L) are seen at Grupo Rev in the Mexican city of Cuernavaca near Mexico City, October 14, 2015. (Photo by Henry Romero/Reuters)

A women wearing a mask to protect from extreme smog visits the Tiananmen Gate in Beijing December 8, 2015 as China's capital issues its first ever "red alert" for pollution. (Photo by Damir Sagolj/Reuters)

Every year, participants in the Burning Man Festival descend on the playa of Nevada's Black Rock Desert to form a temporary city – a self-reliant community populated by performers, artists, free spirits, and more. Last week, an estimated 68,000 people came to Burning Man 2013 from all over the world to dance, express themselves, and take in the spectacle. Gathered below are some of the sights from the festival, which lasted a week and came to its conclusion yesterday