People stroll alongside one of the hills of the Tio Pio park in Madrid, Monday, January 25, 2016. The park is a high viewpoint frequented mostly by locals due to its view of the Spanish capital skyline. (Photo by Francisco Seco/AP Photo)

A dump truck carrying cleaning workers drives on Havana's malecon as a wave crashes on the sea wall, in Cuba, Tuesday, January 24, 2017. Due to high winds and tides, the sea pushed over the sea wall, flooding low parts of the Vedado neighborhood of Havana. (Photo by Desmond Boylan/AP Photo)

High-rise buildings are partly covered by heavy fog at Hong Kong's Victoria Harbour Monday, March 20, 2017. Fog blanketing Hong Kong is common in springtime and may greatly affect shipping and aviation. (Photo by Vincent Yu/AP Photo)

Tourists pose for a selfie in Cancun, October 13, 2015. Cancun's transformation in the 1970s from a small Caribbean fishing village into a strip of nightclubs and high-rise hotels has reduced biodiversity and polluted water resources as infrastructure struggles to keep up. (Photo by Edgard Garrido/Reuters)

Dan Copeland, left, and Alex Morneau of Biddeford, Maine, former high school cheerleaders, perform back flips while enjoying the record breaking heat, Thursday, May 18, 2017, at Old Orchard Beach, Maine. The temperature climbed well into the 90s in many locations throughout the state. (Photo by Robert F. Bukaty/AP Photo)

A sculptural artwork depicting former Chilean dictator Augusto Pinochet and headless presidents shot by a hooded high school student (not pictured) is seen at the Contemporary Art Museum in Santiago, December 2, 2014. The artwork, part of the “El ladrillo angular” (The angular brick) exhibition, portrays a student fighting against the ongoing continuity of dictatorship because of a political and economic system which has been impossible to destroy, according to “Papas Fritas” the artwork's creator. (Photo by Ivan Alvarado/Reuters)

An enterprising Chinese man pulls a bicycle cart packed high with bags of recyclable plastic containers in Shanghai July 25, 2002. The man sells each kilogram (2.2 pounds) of plastic for 0.08 yuan ($.01) to a nearby depot. (Photo by Claro Cortes IV/Reuters)

A pink elephant balloon, one of the entries in the Canadian Hot Air Balloon Championships, lands in a field in High River September 27, 2013. The event is a qualifier for the World Hot Air Balloon Championships in Sao Paulo in 2014. (Photo by Mike Sturk/Reuters)