Iguazu Falls are waterfalls of the Iguazu River on the border of the Brazilian state of Paraná and the Argentinian province of Misiones. The falls divide the river into the upper and lower Iguazu. The Iguazu River rises near the city of Curitiba. It flows through Brazil for most of its course. Below its confluence with the San Antonio River, the Iguazu River forms the boundary between Argentina and Brazil.

A military police officer patrols in the Roquette Pinto shantytown, part of the Mare slum complex in Rio de Janeiro, Brazil, Wednesday, April 1, 2015. The Brazilian army has begun to pull out of one of Rio de Janeiro's most violent slums, with police assuming responsibility for security in the area. (Photo by Felipe Dana/AP Photo)

A Waura Indian woman watches the activities of this year's “quarup”, a ritual held over several days to honour in death a person of great importance to them, in Xingu National Park, Mato Grosso State, August 24, 2013. This year the Waura tribe is honouring their late cacique (chief) Atamai, who died in 2012 and helped created the Xingu Park, and his important contribution in facilitating communication between white Brazilians and Indians. (Photo by Ueslei Marcelino/Reuters)

A woman shouts asking for help during an eviction in Rio de Janeiro, Brazil, Friday, April 11, 2014. Squatters in Rio de Janeiro are clashing with police after a Brazilian court ordered that 5,000 people be evicted from abandoned buildings of a telecommunications company. Officers have used tear gas and stun grenades to try to disperse the families. (Photo by Silvia Izquierdo/AP Photo)

Global wildlife populations will decline by 67% by 2020 unless urgent action is taken to reduce human impact on species and ecosystems, warns the biennial Living Planet Index report from WWF (World Wide Fund for Nature) and ZSL (Zoological Society of London). From elephants to eels, here are some of the wildlife populations most affected by human activity. Here: The maned wolf is among the large mammals in the Brazilian Cerrado that are threatened by the increasing conversion of grasslands into farmland for grazing and growing crops. (Photo by Ben Cranke/Nature Picture Library/Alamy Stock Photo)

A spinning top is seen on a hand during a performance at Sanxia old street in New Taipei City, Taiwan May 8, 2016. Taiwan's ancient folk art of spinning tops is kept alive by a group of enthusiasts who perform intricate tricks with the toys at a temple in Taipei, the capital. (Photo by Tyrone Siu/Reuters)

“Asaro from the Eastern Highlands”. The mudmen could not cover their faces with mud because the people of Papua New Guinea thought that the mud from the Asaro river was poisonous. So instead of covering their faces with this alleged poison, they made masks from pebbles that they heated and water from the waterfall, with unusual designs such as long or very short ears either going down to the chin or sticking up at the top, long joined eyebrows attached to the top of the ears, horns and sideways mouths. (Photo and caption by Jimmy Nelson)

A young boy plays with soap bubbles near Hofburg Palace at Heldenplatz, one of the top tourists attractions in Vienna, Austria, January 26, 2016. (Photo by Christian Bruna/EPA)