Residents observe a police officer take up position during an operation at the Mare slums complex in Rio de Janeiro March 25, 2014. The federal troops have taken control of security operations in Mare slums complex to help quell a surge in violent crime following attacks by drug traffickers on police posts in three slums on the north side of the city, government officials said. (Photo by Ricardo Moraes/Reuters)

An Olympic Airways airplane stands on the premises of the former Athens International airport, Hellenikon June 16, 2014. For about six decades Hellenikon was Athens' only airport but it closed down in 2001 to make way for a newer, more modern airport before the city hosted the 2004 Olympic Games. After languishing for years as a wasteland of crumbling terminals, Hellenikon is set for resurrection as a glitzy coastal resort. Lamda Development, controlled by Greece's powerful Latsis family and leading a consortium of Chinese and Abu-Dhabi based companies, has big dreams for the area since signing a 915 million euro deal for a 99-year lease in March 2014. (Photo by Yorgos Karahalis/Reuters)

In this photo made late Saturday, August 9, 2014, in Keelung, Taiwan, a traditional Chinese dance troupe performs during a parade marking the beginning of the Chinese folklore's mid-summer's Ghost Month Festival. Fourteen days into the seventh month of the lunar calendar, August 9, in 2014, marks the traditional Chinese Ghost Month where the gates of the underworld are opened and spirits of the deceased are set free to roam the world of the living. The month long festivities are aimed to please the roaming spirits. (Photo by Chiang Ying-ying/AP Photo)

Michael Fröhlich's Jowett Javelin rotting car in his forest sculpture park in Neandertal Germany, September 11, 2016. An eccentric artist has collected fifty vintage cars and left them to rot in a forest – and now they're worth over $1 million. Former racing driver Michael Fröhlich, from Dusseldorf, Germany, has purposely crashed the cars into trees, buried them in mud and parked them on cliff faces in his estate's garden in the middle of the German Neanderthal. His collections includes a Jaguar XK120 worth $170,000, a Porsche 356 racer and a Buick worth $17,000. (Photo by Christoph Hagen/Barcroft Images)

An aerial view of a livestock enclosure of the Himba people, in October, 2014, in the Namib Desert, Namibia. A photographer has captured a bird's eye view of the stunning Namib Desert from a paraglider. Theo Allofs travels the world taking stunning pictures of untouched landscapes from a unique perspective. Soaring 300 metres above ground, Theo shot the yellow sand dunes, dry red river beds and remote townships in Namibia. (Photo by Theo Allofs/Barcroft Media)

Aerial photography platform SkyPixel received 27,000 entries to its 2016 competition. Here are the winning shots plus some of our favourites. Here: Dam near perfect. Second prize in the same category was of the Huia Dam in Auckland, New Zealand. Hong Kong-based SkyPixel was launched in 2014. (Photo by Brendon Dixon/SkyPixel)

A man carries an injured girl after what activists said were five air strikes by forces loyal to Syria's President Bashar al-Assad in Douma, eastern al-Ghouta, near Damascus September 11, 2014. (Photo by Bassam Khabieh/Reuters)

Australian Aboriginal hunter Marcus Gaykamangu of the Yolngu people, carries an Australian native lizard called a goanna over his shoulder as he walks away from a billabong near the “out station” of Yathalamarra, located on the outksirts of the community of Ramingining in East Arnhem Land November 22, 2014. (Photo by David Gray/Reuters)