Internally displaced Syrian children stand at the entrance of their makeshift shelter that is an underground cave in Om al-Seer, southern Idlib countryside, Syria December 26, 2015. (Photo by Khalil Ashawi/Reuters)

A woman takes part in a traditional horse parade through the streets of San Jose, Costa Rica December 26, 2015. Thousands of riders participated in the parade, which is part of annual year-end festivities. (Photo by Juan Carlos Ulate/Reuters)

A protester jumps on the table in front of the European Central Bank President Mario Draghi during a news conference in Frankfurt, Germany April 15, 2015. (Photo by Kai Pfaffenbach/Reuters)

A balloon depicting the face of alien movie character E.T. is seen in the sky at the 15th Solar Balloon Festival in Envigado, Colombia December 31, 2015. (Photo by Fredy Builes/Reuters)

Photographer Andy Hall joins the thousands of fans from west Africa who have gathered for Baaba Maal's annual Blues du Fleuve festival in Senegal. Here: Dancers wait to perform on stage. (Photo by Andy Hall/The Observer)

Visitors wear shirts with an image of former Chinese leader Mao Zedong at the Shanghai World Expo site in Shanghai, May 2, 2010. (Photo by Aly Song/Reuters)

A polar bear plays with a pylon during celebrations marking its first birthday in an enclosure at Tierpark Hellabrunn zoo in Munich December 9, 2014. (Photo by Michaela Rehle/Reuters)

Gabriella Papadakis and Guillaume Cizeron of France perform during the ice dance skating event at the ISU Grand Prix of Figure Skating final in Barcelona December 13, 2014. (Photo by Albert Gea/Reuters)