Pope Francis greets the crowd from his popemobile in downtown Rio de Janeiro. Pope Francis touched down in Rio de Janeiro on Monday, starting his first foreign trip as pontiff and a weeklong series of events expected to attract more than a million people to a gathering of young faithful in Brazil, home to the world's largest Roman Catholic population. (Photo by Ueslei Marcelino/Reuters)

A man runs after he tried to put himself on fire during a protest at a makeshift camp at the Greek-Macedonian border near the village of Idomeni on March 22, 2016. Greece will not be able to start sending refugees back to Turkey from March 20, 2016, the government said, as the country struggles to implement a key deal aimed at easing Europe's migrant crisis. The numbers are daunting: officials said as of Saturday there were 47,500 migrants in Greece, including 8,200 on the islands and 10,500 massed at the Idomeni camp on the Macedonian border. (Photo by Andrej Isakovic/AFP Photo)

About a dozen dogs traded in their leashes for life vests Saturday for the chance to ride the waves at Jupiter beach as part of a canine surfing competition to raise money for an animal rescue group. Photo: Musso paddles in with Jengo. (Photo by Taylor Jones/The Palm Beach Post)

In Dougie Wallace’s photos of Mumbai taxis, the chatter, yelling, and constant horns of the city are almost audible. A selection of his images is on show at Gayfield Creative Spaces, Edinburgh, as part of the Retina photography festival until 30 July. For four years, the Glasgow-born Wallace focused his photos on one kind of taxi in particular: the Premier Padmini, a 1960s workhorse painted in black and yellow. Locally known as “Kaali-Peeli”, there were once more than 60,000 of them in the Indian city. But thanks to laws restricting pollution, the cars now are fast disappearing from Mumbai’s streets. (Photo by Dougie Wallace/The Guardian)

Fashionistas pose for photographs in front of a homeless man outside Moynihan Station following a showing of the Rag & Bone Spring/Summer 2013 collection during New York Fashion Week in this September 7, 2012 file photo. (Photo by Lucas Jackson/Reuters)

Thomas Thwaites of the United Kingdom accepts the 2016 Ig Nobel Prize in Biology for “creating prosthetic extensions of his limbs that allowed him to move in the manner of, and spend time roaming the hills in the company of, goats” during the 26th First Annual Ig Nobel Prize ceremony at Harvard University in Cambridge, Massachusetts, U.S. September 22, 2016. (Photo by Brian Snyder/Reuters)

Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)