Roof-topping enthusiast Daniel Lau takes a selfie with high-rise buildings down below as he stands on the top of a skyscraper in Hong Kong, China on August 15, 2017. A craze that began in Russia has now taken hold in Hong Kong, one of the world's most vertical cities. Mr Lau said he had been inspired by Russian climbers and that he was unafraid of the vertiginous heights he scales. (Photo by ImagineChina/Rex Features/Shutterstock)

“Two Brothers”. We found about 20 lions eating a buffalo. When the male leaved the group we anticipated him to take photos. It is 8AM, light is perfect and the position too. The lion stops and looks down from the hill, another lion is coming up, it stiffens, I think that will be a fight, i'm tense, the camera is OK, the shots previously made perfect. The two meet, looking directly into their eyes, they sniff, rub against their heads, the tension drops, they start walking with the same step as when they were puppies, they are two brothers. Photo location: Masai Mara, Kenya. (Photo and caption by Massimo Mei/National Geographic Photo Contest)

“Penguin Highway” in Antarctica by Melissa Brennan (Video by Melissa Brennan). Very funny, I recommend to look! =)

Guardian of the Mangroves – Overall Winner. Tanya Houppermans, Cuba. A curious American crocodile (Crocodylus acutus) swims right up to Tanya, at Gardens of the Queen (Jardines De La Reina), an archipelago off the coast of Cuba. It has been strictly protected since 1996, and is one of the most untouched marine ecosystems in the world. ‍ “The healthy population of American crocodiles is down to the pristine condition of the mangroves and I wanted to capture close ups of this gentle giant in its natural habitat. I hope this image can illustrate that protecting areas like this is so critical”. (Photo by Tanya Griffin Houppermans/Mangrove Photographer of the Year)

Second Place Winner: “Thunderstorm at False Kiva”. I hiked out to these ruins at night hoping to photograph them with the Milky Way, but instead a thunderstorm rolled through, creating this dramatic image. – Max Seigal. National Geographic Traveler Director of Photography Dan Westergren, one of this year's judges, shares his thoughts on the second place winner: “This photo combines two different scenes into one: the small kiva in a cliff dwelling and the grand vista of Canyonlands National Park across the valley. I really like the two different color palettes – warm inside and purple outside. This two-for-one scene was caused by the lightning storm outside the dwelling, which lit up the landscape like it was a huge electronic flash. Looking at this picture I can imagine what a wonderful sight it must have been for the ancient people who lived here. It doesn't seem too amazing now in our modern world, but might have been mind-blowing for the prehistoric residents”. Location: Utah. (Photo and caption by Max Seigal/National Geographic Traveler Photo Contest)

“Hi! My name is Seiji Mamiya. I hope my cat pictures would make you all happy!”

A Japanese white-eye is seen on a branch of cherry blossoms at Kyoto Imperial Palace on March 26, 2010 in Kyoto, Japan. (Photo by Akihiro I/Getty Images)