A tourist poses for a picture with the Sphinx at the Pyramids of Giza in Cairo, Egypt, on October 19, 2011. (Reuters/Jamal Saidi)

Participants wear traditional clogs as shepherds lead their sheep through the center of Madrid, October 28, 2012. (Photo by Andres Kudacki/Associated Press)

Students pose for a pictures taken by their friends during spring break on the beach in the resort city of Cancun, Mexico, February 27, 2009. (Photo by Israel Leal/AP Photo)

Denver Broncos cheerleaders during the third quarter. The Denver Broncos played the Kansas City Chiefs at Sports Authority Field at Mile High in Denver, Colo. on September 14, 2014. (Photo by Aaron Ontiveroz/The Denver Post via Getty Images)

Participants wearing masks during a hazy day at the Beijing International Marathon in front of Tiananmen Square, in Beijing, October 19, 2014. (Photo by Reuters/Stringer)

Juri Mitomi, 20, holds a cigarette after a Coming of Age Day celebration ceremony at an amusement park in Tokyo January 12, 2015. According to a government announcement, more than 1.2 million men and women who were born in 1994 marked the coming of age this year, an increase of approximately 50,000 from last year. The increase is also the first since 1995. (Photo by Yuya Shino/Reuters)

Injured horses huddle together in Oklahoma City on Monday. (Photo by Chris Landsberger/The Oklahoman)