Farmers clash with riot policemen during a protest outside the Greek Agriculture Ministry on March 8, 2017 in Athens, Greece. Two people were detained after the windows of two police vans were smashed as approximately 1,000 farmers, mainly from the island of Crete, took part in the protest. (Photo by Nikolas Georgiou/ZUMA Wire/Rex Features/Shutterstock)

In this March 22, 1975 file photo, a refugee clutches a baby as a government helicopter gunship carries them away near Tuy Hoa, Vietnam, 235 miles northeast of Saigon. They were among thousands fleeing from Communist advances. AP Photographer Nick Ut will be retiring from the AP in March 2017 after 51 years of taking photographs from the front lines of the Vietnam War to the red carpets of Hollywood. (Photo by Nick Ut/AP Photo)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Revellers enjoy air temperatures near freezing as they participate in the annual New Year's polar bear dip in the icy waters of Charlottetown harbour on Wednesday, January 1, 2020, in Charlottetown, Prince Edward Island. (Photo by Andrew Vaughan/The Canadian Press via AP Photo)

“These Rajasthani sisters were sitting on the staircase inside their house relaxing and enjoy a cup of masala chai”. (Photo by Firdaus Hadzri/National Geographic Travel Photographer of the Year Contest)

A Rohingya refugee girl named Rufia Begum, aged 9, poses for a photograph as she wears thanaka paste at Balukhali camp in Cox's Bazaar, Bangladesh, March 31, 2018. (Photo by Clodagh Kilcoyne/Reuters)

A couple embrace during the start of the San Fermin festival in Pamplona, Spain July 6, 2016. Revelers from around the world kick off the festival with a messy party in the Pamplona town square, one day before the first of eight days of the running of the bulls. (Photo by Vincent West/Reuters)

A kid from Sichuan provice smokes at an assistance center February 23, 2005 in Shenzhen, Guangdong Province, China. The kids, ranging in age from 7 to 16, are temporary residents of the center, one of the institutions established by China's departments of civil affairs to help and administer beggars, vagrants and juvenile delinquents, after rescission of China's compulsory detainment and relocation system. (Photo by Cancan Chu/Getty Images)