Polar bear cubs looking out of their den in Wapusk National Park, Manitoba, Canada (© Robert Harding/Alamy)

Clouds flowing over the mountains of Tenerife, Canary Islands, Spain (© MikeMareen/iStock/Getty Images Plus)

榕树上的幽灵眼镜猴，印度尼西亚Tangkoko Batuangus自然保护区 (© Ondrej Prosicky/Shutterstock)

Spectral tarsiers in a ficus tree in Tangkoko Batuangus Nature Reserve, Indonesia (© Ondrej Prosicky/Shutterstock)

科罗纳多国家森林里的巨柱仙人掌花，亚利桑那 (© Jack Dykinga/Minden Pictures)

Saguaro cactus flowers, Coronado National Forest, Arizona (© Jack Dykinga/Minden Pictures)

Male mountain bluebird in Yellowstone National Park, Wyoming (© Jason Savage/Tandem Stills + Motion)

The Falls of Bruar, Perthshire, Scotland (© Peter Watson/Superstock)

The Joan of Arc Monument at Riverside Park in Manhattan, New York City (© Chase Guttman/Alamy)

Grizzly bear cub relaxing, Cook Inlet, Chinitna Bay, Lake Clark National Park, Alaska (© Erlend Krumsvik/Getty Images)

Milky Way over hoodoo rock formations in the Canadian Badlands, Drumheller, Alberta, Canada (© Felis Images/Minden Pictures)

Brighton Jetty in Brighton, Adelaide, Australia (© Darryl Leach/Alamy)

Sunrise at Angkor Wat in Cambodia (© Sergio Diaz/Getty Images)

A heron perches on a piling at the Salton Sea in California (© Garret Suhrie/Cavan Images)

Sunrise at Loughrigg Tarn, Ambleside, Lake District, England (© John Finney photography/Getty Images)

Local women climbing a stepwell near Amber Fort in Jaipur, Rajasthan, India (© Shanna Baker/Offset)

Lenticular clouds over Mount Rainier, Washington (© Delrious/Shutterstock)

European bee-eaters in the Extremadura region of Spain (© Martin Demmel/Offset)

The Radcliffe Camera, Oxford, England (© Joe Daniel Price/Getty Images)

Azaleas in bloom at Magnolia Plantation and Gardens, Charleston, South Carolina (© Joanne Wells/Danita Delimont)

Formentor Lighthouse at the tip of Cap de Formentor, Mallorca, Spain (© Lasse Eklöf/DEEPOL by plainpicture)

A European crested tit weathers a storm in Scotland (© Ben Hall/Minden Pictures)

Blooming cherry trees in Vancouver, B.C., Canada (© Bun Lee/Getty Images)

Carrick-a-Rede rope bridge connecting two cliffs near Ballintoy, County Antrim, Northern Ireland (© NordicMoonlight/iStock/Getty Images Plus)