Boys play basketball in the facilities of Belarus' Republican Clinic of Speleotherapy within a salt mine, as part of their treatment, near the town of Soligorsk, south of Minsk, February 19, 2015. According to the state clinic, more than 7,000 children and adults seek medical treatment for respiratory illness each year in the subsurface chambers of its facilities, located 420 metres underground between layers of potassium and stone salts in an operational salt mine. (Photo by Vasily Fedosenko/Reuters)

Participants demonstrate for the media before the role play event at Czocha Castle in Sucha, west southern Poland April 9, 2015. Harry Potter enthusiasts from all over the world are attending a four-day live action role play event at the medieval castle made into a close imitation of the “College of Wizardry”. (Photo by Kacper Pempel/Reuters)

An employee works on the automobile assembly line of a Citroen C3 car at the PSA Peugeot Citroen plant in Poissy, near Paris, France, April 29, 2015. PSA Peugeot Citroen said on Wednesday its revenue rose in the first quarter as the recovering French carmaker's efforts to raise prices helped offset weaker volumes. (Photo by Benoit Tessier/Reuters)

A reveller, covered in mud, chats with friends during the Glastonbury Festival at Worthy Farm in Somerset, Britain, June 26, 2015. The outdoor festival runs from 24 to 29 June. (Photo by Dylan Martinez/Reuters)

A walruses at Hagenbeck Zoo in Hamburg, Germany on July, 7, 2015. (Photo by Werner Struss/Startraks action)

A Japanese Ground Self-Defense Force Type 92 Mine sweeping vehicle fires a rocket behind a Type 74 armoured tank during an annual training session, which is based on a scenario to defend or retake islands in Japanese territory, near Mount Fuji at Higashifuji training field in Gotemba, west of Tokyo, August 18, 2015. (Photo by Yuya Shino/Reuters)

Guests have breakfast as another guest climbs to gather at the Skylodge Adventure Suites in the Sacred Valley in Cuzco, Peru, August 14, 2015. Tourists taking on an arduous climb up the steep cliff face of Peru's Sacred Valley are being rewarded for their efforts by being able to spend the night in transparent mountaintop sleeping pods at the “Skylodge Adventure Suites”. To reach the pods, visitors need to climb 400 metres of via ferrata (a steel cable and rungs) up the valley side or hike an intrepid trail through zip lines. (Photo by Pilar Olivares/Reuters)

A picture made with a tilt-shift lens shows “Dwarf Empire” cast member 19-year-old Han Zhen Yan posing in her fairy costume backstage outside one of the fairy tale-like houses at the Dwarf Empire theme park outside Kunming, China's Yunnan province, 04 April 2013. The Dwarf Empire theme park opened in mid-2009, employing a number of dwarves to create the show. Depending on what type of job they do at the park, employees earn between 800-2,000 CNY (100-250 Euros) per month, most of which goes towards their savings as lodging is provided, and their living quarters are equipped with kitchens where they prepare their own meals. (Photo by Diego Azubel/EPA)