In Omdurman, the largest city in Sudan, the Qadiriyya Sufi order meets every Friday outside Sheikh Hamed Al Nil mosque, which houses the tomb of their 19th century Sufi leader. (Photo by Ala Kheir, John Burns and Ibrahim Algrefwi/Brownbook)

A girl lights a candle as she marks the anniversary of 2015 Nepal earthquake, at Boudhanath stupa in Kathmandu, Nepal April 25, 2017. (Photo by Navesh Chitrakar/Reuters)

This picture taken on May 23, 2017 shows visitors posing for photos along a path at an Indonesian hamlet dubbed “the rainbow village” in Semarang, central Java, that has become an internet sensation and attracting hordes of visitors. (Photo by Suryo Wibowo/AFP Photo)

Humanoid robot bartender “Carl” interacts with guests at the Robots Bar and Lounge in the eastern German town of Ilmenau, July 26, 2013. “Carl”, developed and built by mechatronics engineer Ben Schaefer who runs a company for humanoid robots, prepares spirits for the mixing of cocktails and is able to interact with customers in small conversations. (Photo by Fabrizio Bensch/Reuters)

Pod of dolphins surf effortlessly through the waves in the wild traveling at speeds up to 20 mph. (Photo by Greg Huglin)

Yalena Leuliette, 7, of Greenbelt, Md., throws seeds from a cattail plant up in the air as she plays while visiting the Kenilworth Aquatic Gardens in northeast Washington, on Sunday, August 9, 2015. Leuliette visits the public garden with her parents a few times a year. (Photo by Jacquelyn Martin/AP Photo)

When it opened in 1955, the Grande Hotel in the Indian Ocean city of Beira was one of the most luxurious in Africa. Photojournalist Fellipe Abreu documents the lives of the 3,500 people who now fill this long-closed hotel to capacity. (Photo by Fellipe Abreu/The Guardian)

A boat sails behind a woman looking through binoculars as she sits on a cliff on a sunny day in Sydney, Australia, May 29, 2016. (Photo by David Gray/Reuters)