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)

Expedition 44 flight engineer and NASA astronaut Scott Kelly seen inside the Cupola, a special module which provides a 360-degree viewing of the Earth and the International Space Station. Kelly is one of two crew members spending an entire year in space. (Photo by Scott Kelly/NASA)

Visitors to the annual Vivid Sydney light festival wear matching illuminated suits alongside the Sydney Harbour Bridge on the second night of the light and sound show in Sydney, Australia, May 28, 2016. (Photo by Jason Reed/Reuters)

A woman sports a rainbow painted hand at the annual PrideFest celebration at Civic Center Park in Denver, Colorado June 18, 2016. (Photo by Andy Cross/The Denver Post)

A string is used to ensure that the skirts of female members of the honour guard are in the same height from the ground as they prepare for a welcoming ceremony for Congo Republic President Denis Sassou Nguesso outside the Great Hall of the People in Beijing, China, July 5, 2016. (Photo by Jason Lee/Reuters)

Revellers chat on Havana's Malecon seafront before performing at a carnival parade, Cuba, August 12, 2016. (Photo by Alexandre Meneghini/Reuters)

In this September 1, 2016 photo, 90-year-old street vendor Antonio Bauza waits for tourists to sell his bananas, next to the village church in Remedios, Cuba. With the arrival of the first commercial flights from the U.S. to Cuba in more than 50 years, the Cuban government is welcoming the wave of new visitors and struggling to update infrastructure that's already overwhelmed. (Photo by Ramon Espinosa/AP Photo)

Lightning strikes during a storm over the Ionian Sea in Calabria, Italy on June 27, 2016. (Photo by Alfonso Di Vincenzo/Pacific Press/Rex Features)