Tourists take a “selfie” as demonstrators burn a trash container during a May Day rally in Barcelona, Spain, on May 1, 2014. Tens of thousands of workers marked May Day in European cities with a mix of anger and gloom over austerity measures imposed by leaders trying to contain the eurozone's intractable debt crisis. (Photo by Manu Fernandez/Associated Press)

Visitors and a dog stand on the new “Skywalk” viewing platform on the Sonnenstein mountain in the Eichsfeld region near Bad Lauterberg im Harz, central Germany, on May 22, 2017. (Photo by Martin Schutt/AFP Photo/DPA)

2016 Rio Olympics, Athletics, Women's Heptathlon Javelin Throw, Groups, Olympic Stadium, Rio de Janeiro, Brazil on August 13, 2016. Evelis Aguilar (COL) of Colombia competes in Javelin group A women's heptathlon. (Photo by Dylan Martinez/Reuters)

A reveller dressed as Spider-Man takes part in a presentation at the top of a building during an annual block party known as “Enquanto isso na Sala da Justiça” (Meanwhile, in the justice room), one of the many carnival parties taking place in the neighbourhood of Olinda, Brazil February 7, 2016. (Photo by Ueslei Marcelino/Reuters)

Women take a photo in the late afternoon sun during the Coachella Valley Music and Arts Festival on April 17, 2017 in Indio, California. (Photo by Carlo Allegri/Reuters)

A girl watches an acrobatic performance at the Longtan park as the Chinese Lunar New Year, which welcomes the Year of the Monkey, is celebrated in Beijing, China February 9, 2016. (Photo by Damir Sagolj/Reuters)

Participants share a moment after performing at a cultural program during India's Independence Day celebrations in Ajmer, in the desert state of Rajasthan, India, August 15, 2016. (Photo by Himanshu Sharma/Reuters)

In this March 14, 2015 photo, tourists take pictures from a viewing area at Iguazu Falls in Brazil. From walkways and bridges, viewers can count 270 water falls almost 100 meters (330 feet) high. (Photo by Jorge Saenz/AP Photo)