Romanian military doctors and medical students sit on a bus behind steamy windows before the National Day parade in Bucharest, Romania, Thursday, December 1, 2016. Military planes and helicopters flew over the Romanian capital Thursday as thousands turned out to celebrate the national day, marking the date when the country reunified with Transylvania in 1918. (Photo by Vadim Ghirda/AP Photo)

South Asian countries in terms of total contribution of travel and tourism to GDP. #6. Vietnam, Total GDP: USD 202.6 billion (2016). Contribution of Travel and Tourism to GDP: 9.1% . Here: A boat in the Thu Bon River, Hoi An, Vietnam. (Photo by Domingo Leiva/Getty Images)

Geology Professor Fetullah Arik takes measurements next to a large sinkhole on June 03, 2021, in Karapinar, Turkey. In Turkey’s Konya province, the heart of the country's agriculture sector, extreme drought conditions over the past two years are taking a heavy toll on farmers and the land. (Photo by Chris McGrath/Getty Images)

For more than three years, Ukraine has been plagued by a conflict between the eastern secessionist territories and the Kiev government. Demonstrations by pro-Russian parties that oppose the current government first began in 2014 - and now, over 10,000 people have died, many of them civilians. These images portray a generation caught between war and peace. Many of them were born into the civil conflict dominating the country and are disorientated about their place in the world. Here: Youths during a party organised on a decommissioned bridge in Kiev. (Photo by Aude Osnowycz/The Guardian)

The competition is run by Royal Observatory Greenwich sponsored by Insight Investment and in association with BBC Sky at Night Magazine. This year astrophotographers from 91 countries sent in more than 4,200 spectacular entries. Here: The Milky Way rises above an isolated lighthouse in Tasmania. Shot by James Stone of Australia. (Photo by James Stone/Astronomy Photographer of the Year 2018)

Photographer Han Youngsoo captured the ordinary people of Korea as the country emerged from war into an age of prosperity. Han Youngsoo: Photographs of Seoul 1956–63 is at the International Center of Photography (ICP), Jersey City, New Jersey, until June 9, 2017. Here: Seoul, Korea. (Photo by Han Youngsoo/The Guardian)

In this Sunday, March 12, 2017, picture a Don Sphinx cat reaches for a judge while being evaluated, in Bucharest, Romania. More than 1,500 dogs and 150 cats from twelve countries were evaluated during a three day pet show and competition in the Romanian capital. (Photo by Vadim Ghirda/AP Photo)

A dancer performs before a judging panel during the World Irish Dancing Championships in Dublin, Ireland on April 11, 2017. The April 9-16 event draws some 5,000 performers from Ireland and overseas, including from both the Irish diaspora in places like the United States and Australia as well as less likely countries such as Russia and Japan. (Photo by Clodagh Kilcoyne/Reuters)