A huge colony of Pacific Walrus on Arakamchechen Island in the Northern Bering Sea. (Photo by Francois Gohier/Ardea/Caters News)

Two women look at a mobile phone as they stand on Tiananmen Square during a sand storm in heavily polluted weather in Beijing on February 28, 2013. Beijing residents were urged to stay indoors as pollution levels soared before a sandstorm brought further misery to China's capital. (Photo by Ed Jones/AFP Photo)

This 2014 series Shanghai Tian Wa saw Chinese photographer Liu Tao train his lens on two distinct districts in Shanghai. Here: “Shanghai Tian Wai №26, 2014”. (Photo by Liu Tao/The Guardian)

Young category winner. Great autumn morning by Fabian Dalpiaz. (Photo by Fabian Dalpiaz/2018 Astronomy Photographer of the Year)

This week's full Moon as photographed from on board the International Space Station by NASA astronaut Jeff Williams on August 19, 2016. Jeff is currently Commander of the Space Station for the Expedition 48 crew. (Photo by Jeff Williams/NASA)

A donkey carrying sacks of coal walks through the narrow tunnels of a coal mine, in Choa Saidan Shah in Punjab province April 29, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. (Photo by Sara Farid/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

“The September 11 attacks (called September 11, September 11th or 9/11), were a series of four coordinated suicide attacks against targets in New York City and the Washington, D.C. area on September 11, 2001. On that morning, 19 terrorists from the Islamist militant group al-Qaeda hijacked four passenger jets. The hijackers intentionally crashed two planes into the Twin Towers of the World Trade Center in New York City; both towers collapsed within two hours. Hijackers crashed a third plane into the Pentagon in Arlington, Virginia. When passengers attempted to take control of the fourth plane, United Airlines Flight 93, it crashed into a field near Shanksville, Pennsylvania, preventing it from reaching its intended target in Washington, D.C. Nearly 3,000 died in the attacks”. – Wikipedia

Photo: A firefighter breaks down after the World Trade Center buildings collapsed September 11, 2001 after two hijacked airplanes slammed into the twin towers in a terrorist attack. (Photo by Mario Tama/Getty Images)