The 26th annual National Geographic Traveler Photo Contest is now accepting submissions. Official categories include: “Travel Portraits”, “Outdoor Scenes”, “Sense of Place” and “Spontaneous Moments”. The contest is accepting entries until June 30. Photo: “Forest lights”. Aurora Borealis over the forest of the Pyhae Luosto National Park, Finland. (Photo and caption by Nicholas Roemmelt/National Geographic Traveler Photo Contest)

These stunning pictures show a normally vicious tiger calmly swimming in a pool of algae, on Jule 9, 2014. The powerful cat takes a refreshing break by taking a dip in the bright green algae. But it looks like this big cat is scared of getting his head wet as he strains to keep it above the water. After splashing around for a bit the tiger gets out and tries to air-dry with specks of the vegetation dripping off his fur. The striking pictures were taken at Copenhagen zoo by snapper Soren Lundgren Neilson. (Photo by Soren Nielsen/Caters News)

Four year old Kaleb Stanley (R), from Dublin, reaches up to puncture a giant bubble with the help of his seven year old brother Jacob on London's South Bank on May 9, 2008 in England. (Photo by Peter Macdiarmid/Getty Images)

“For most Londoners, the most common view they enjoy as they trudge to work is the back of another commuter's head. But now, thanks to the Streetmuseum app, anyone traipsing through the capital's streets can step back in time to see what London looked like in the 19th and 20th century compared with today – all in the same image”. – Joe Krishnan via The Independent. Photo: A street scene in London’s Covent Garden with the underground station and a horse and cart in the background in c.1930 and the same street in 2014. (Photo by Museum of London/Streetmuseum app)

Firefighting teams try to extinguish an oil fire November 27, 2016 as smoke billows from one of the remaining oil wells set ablaze by ISIL in their retreat from Qayyarah at the start of the Mosul offensive which began more than a month prior. (Photo by Byron Smith/ZUMA Wire/Rex Features/Shutterstock)

A Iraqi soldier of the 9th division is seen within a Humvee in Shyma district in Mosul, Iraq, Tuesday, December 6, 2016. Iraqi forces, backed by the U.S.-led international coalition, launched a campaign in October to retake Mosul, the country's second largest city and IS's last major urban bastion in Iraq. (Photo by Manu Brabo/AP Photo)

A sales assistant poses for photographs with a mealworm cookie in Seoul, South Korea, August 8, 2016. Insect-eating, or entomophagy, has long been common in much of the world, including South Korea, where boiled silky worm pupae, or beondegi, are a popular snack. Now, South Korea is looking to expand its insect industry as a source of agricultural income. (Photo by Kim Hong-Ji/Reuters)

A vervet monkey passes in front of a woman on the shores of lake Naivasha, Kenya January 24, 2017. (Photo by Goran Tomasevic/Reuters)