A view of Worker and Kolkhoz Woman, a sculpture by Vera Mukhina, at the main entrance to Moscow's VDNKh exhibition center in Moscow, Russia on September 27, 2017. (Photo by Dmitry Serebryakov/TASS/Barcroft Images)

A combination photo shows various popular street foods under $6 from various hawker food stalls and eateries in Singapore, taken between July 28 to 31, 2016. Top row (L to R) bak chor mee, soya sauce chicken; Middle row (L to R) laksa, hokkien mee, nasi lemak, ice kachang; Bottom row (L to R) rojak, roti prata and satay. (Photo by Edgar Su/Reuters)

It might have been foggy in the Willamette Valley, but Cerridwen Martin was able to revel in a view of the top of the clouds from the summit of Spencer Butte in Eugene, Ore., on Tuesday, December 16, 2014. Martin was joined by Joe Martinson, right, for the 1.1 mile trek. Fog shrouded much of the city for most of the day. (Photo by Andy Nelson/AP Photo/The Register-Guard)

A mahout watches the Thai animation movie Kan Kluay with his elephant in Ayuthaya province, about 80km (49 miles) north of Bangkok June 5, 2006. The movie tells the story of a young Thai wild elephant who, while looking for his father, becomes the war elephant of the Thai King fighting against Burma and restored Thailand's ancient Ayuthaya empire that existed about 400 years ago. (Photo by Sukree Sukplang/Reuters)

A man poses with a hyena along a street in Lagos, Nigeria November 4, 2008. (Photo by Akintunde Akinleye/Reuters)

A pilot inflates a hot air balloon while taking part in the 38th International Balloon Festival of Chateau-d'oex, Switzerland, 23 January 2016. The festival takes place from 23 to 31 January. (Photo by Vincent Vannay/EPA)

The first autonomous and electric shuttle of PostAuto Schweiz in the old village of Sion, Switzerland, June 2016. (Photo by Ruben Sprich/Reuters)