The Imperial Russian Ballet members wait to perform Tchaikovsky's “Swan Lake” at Arena hall in central Bosnian town of Zenica December 7, 2014. (Photo by Dado Ruvic/Reuters)

A young boy plays with soap bubbles near Hofburg Palace at Heldenplatz, one of the top tourists attractions in Vienna, Austria, January 26, 2016. (Photo by Christian Bruna/EPA)

People hold umbrellas as they walk past a flooded street in Taiyuan, Shanxi Province, China, July 19, 2016. (Photo by Reuters/China Daily)

Sunrise over a moor viewed from Littaford Tor, Dartmoor, UK, 2016. Autumn visits the windswept moors and granite tors of Dartmoor earlier than the rest of the south-west. While there aren’t many trees here, autumn shades appear in golden ferns and tan heather. Littaford Tors, near Two Bridges and a mile from Princetown, is a short walk and can be combined with a visit to the adjacent Wistman’s Wood. (Photo by Stuart Holmes)

Woman on phone in hotel room. (Photo by DreamPictures/Getty Images)

In this picture taken on November 28, 2016, a hot-air balloon carrying tourists sails over the archeological site at sunrise in Bagan. Located in central Myanmar, Bagan is home to more than 2,000 ancient Buddhist monuments deeply revered in the Buddhist-majority nation and is one of the country's most popular tourist destinations. (Photo by Dale De La Rey/AFP Photo)

A woman dressed up for Halloween travels on a Metro train in São Paulo, Brazil on October 30, 2017. (Photo by Cris Faga/Rex Features/Shutterstock)

The Royal Castle is seen a veil of heavy winter smog in Budapest, Hungary on January 30, 2017. (Photo by Laszlo Balogh/Reuters)