Members of Brazil's Movimento dos Sem-Teto (Roofless Movement) stand in the hallway of one of the 11 empty buildings that the movement took over recently, in the centre of Sao Paulo, November 6, 2012. According to City Hall, there are some 400,000 people in need of stable housing, including the 4,000 families of the Roofless Movement who are squatting in abandoned or vacant buildings that range from apartment blocks to hotels, in Sao Paulo, the largest city in South America. (Photo by Nacho Doce/Reuters)

“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)

A bunker at aformer Swiss artillery fortress called Heldsberg stands near the town of St. Margareten, Switzerland March 22, 2015. Heldsberg fortress, located on the Swiss-Austrian border near the River Rhine and Lake Constance was built from 1938 to 1940 and remained in military use until 1992. Since 1993 it is open to the public as Fortress Museum Heldsberg. (Photo by Arnd Wiegmann/Reuters)

These romantic sepia shots show lovers enjoying quiet, unguarded moments together – but the subjects are not besotted couples; they are fearsome big cats. Freelance snapper Goran Anastasovski has devoted more than 10 years of his life to photographing big cats and other animals. The 46-year-old from Macedonia aims to emphasize their human qualities in his photographs. (Photo by Goran Anastasovski/Caters News)

In this January 12, 2016 photo, an abandoned boat lies on the dried up lake bed of Lake Poopo, on the outskirts of Untavi, Bolivia. Drought caused by the recurrent El Nino meteorological phenomenon is considered the main driver of the lake's demise. Along with glacial melting, authorities say another factor is the diversion of water from Poopo's tributaries, mostly for mining but also for agriculture. (Photo by Juan Karita/AP Photo)

This picture taken on January 26, 2016 shows a monkey sitting on a bench during rehearsal at a monkey training school in a zoo in Dongying, eastern China's Shandong province. Shows featuring performing simians, popular in China and throughout Asia, are expecting a boost in the Lunar New Year of the monkey, which begins on February 8. But they are facing a growing backlash from Chinese people concerned about animal welfare. (Photo by Wang Zhao/AFP Photo)

Thanks to plenty of salt minerals and heavy elements in the soil, the Dallol volcano in Ethiopia produces brilliantly colored pools of water at the top of its caldera. And, as if to add greater effect to the already stunning sights, the volcano stands apart from the salt plains around it like an island. This hotspot was created through phreatomagmatic eruptions caused by magma interacting with water, and was further altered due to the presence of salt water. (Photo by Francisco Pandolfo/Caters News)

A rebel fighter supporter shoots an AK-47 rifle as she reacts to the news of the withdrawal of Libyan leader Muammar Gaddafi's forces from Benghazi March 19, 2011. The conflict was sparked by clashes in Benghazi and escalated into a rebellion that spread across the country. Gaddafi was captured and killed on October 20, 2011. Libya is currently caught up in a conflict between two rival factions who once battled together against the late Libyan leader. (Photo by Goran Tomasevic/Reuters)