A worker carries a bag of salt after collecting it from a pond at the Maras mines in Cuzco December 3, 2014. Salt has been obtained in Maras since pre-Incan times by evaporating highly salty local subterranean stream water. The water is intricately channelled through constructions, flowing gradually down onto several hundred ancient terraced ponds. From each pond, a local member of the mine cooperative can produce 150 to 200 kilos per month which can be sold in the markets at $0.34 per kilogram, according to miners. (Photo by Enrique Castro-Mendivil/Reuters)

In this January 31, 2014 file photo released by the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA), shows residents of the besieged Palestinian camp of Yarmouk, queuing to receive food supplies, in Damascus, Syria. That year, the U.N. was able to deliver food to about five percent of people in besieged areas including Yarmouk, while today estimates show the organization is reaching less than one percent. (Photo by UNRWA via AP Photo)

In northwest Russia, in a small village called Alekhovshchina, Nadia Sablin's aunts spend the warmer months together in the family home and live as the family has always lived, chopping wood to heat the house and making their own clothes. Sablin's book of photographs, “Aunties: The Seven Summers of Alevtina and Ludmila”, is published by Duke University Press. Here: “Two-Handed Saw, 2014”. (Photo by Nadia Sablin)

A fighter jet flies above as Ukrainian soldiers sit on an armoured personnel carrier in Kramatorsk, in eastern Ukraine April 16, 2014. Ukrainian government forces and separatist pro-Russian militia staged rival shows of force in eastern Ukraine on Wednesday amid escalating rhetoric on the eve of crucial four-power talks in Geneva on the former Soviet country's future. (Photo by Marko Djurica/Reuters)

Balal, who killed Iranian youth Abdolah Hosseinzadeh in a street fight with a knife in 2007, is brought to the gallows during his execution ceremony in the northern city of Nowshahr on April 15, 2014. The mother of Abdolah Hosseinzadeh spared the life of the her son's convicted murderer, with an emotional slap in the face as he awaited execution prior to removing the noose around his neck. (Photo by Araash Khamooshi/AFP Photo/ISNA)

Rio de Janeiro's state military policemen aim their guns during a violent protest in a favela next to Copacabana, Rio de Janeiro on April 22, 2014. Violent protests broke out in Rio's landmark beachfront district, Copacabana, following the death of a resident last weekend during clashes with the Army in a nearby favela. (Photo by Christophe Simon/AFP Photo)

A man wearing a “Pinhead” mask walks through the grounds of St Mary's Church, Whitby, during the Whitby Gothic festival taking place this weekend, on April 27, 2014. The twice yearly event attracts Goths from across the UK and beyond to the historic fishing town and is a great boost to the local economy. (Photo by Anna Gowthorpe/PA Wire)

A tour group wanders through block 7 of Eastern State Penitentiary in Philadelphia, Pennsylvania April 30, 2014. Opened in 1829, with the original corrective system of “confinement in solitude with labor”, the penitentiary housed about 75,000 inmates in its 142 years of operation. At Eastern State reunions, former inmates, staff and guard gather to share memories and trade stories and get a chance to describe their experiences in question-and-answer sessions with the public. (Photo by Mark Makela/Reuters)