The whirlpool in Myllykoski scenic area at winter in Oulanka National Park, Kuusamo, Finland (© Lassi Rautiainen/Minden Pictures)

'Field of Light at Sensorio,' by Bruce Munro, Paso Robles, California, USA. (© George Rose/Getty Images)

Sperm whale mother and albino baby swimming off the coast of Portugal (© Flip Nicklin/Minden Pictures)

Trakai Island Castle Museum in Trakai, Lithuania (© Andrius Aleksandravicius/Alamy)

Moons of Jupiter—Io, Europa, Ganymede, and Callisto (© Branko Šimunek/Alamy)

Tianmen Mountain in Zhangjiajie, China (© Bogdan Dyiakonovych/Shutterstock)

Muir Woods National Monument, San Francisco, California, USA (© Mia2you/Shutterstock)

Flags outside the UN's Palace of Nations in Geneva, Switzerland (© Mustafa Yalcin/Anadolu Agency/Getty Images)

Small rakan statues line the stone pathway to the Daisho-in Temple, Miyajima, Japan (© Malcolm Fairman/Alamy)

Eibsee lake at the base of Zugspitze mountain, Bavaria, Germany (© Marc Hohenleitner/Huber/eStock Photo)

Aerial view of Boudhanath stupa in Kathmandu, Nepal (© Maksim Semin/Shutterstock)

Male muskoxen near Prudhoe Bay in Alaska, USA (© Oliver Smart/Alamy)

Pongal kolam in Tamil Nadu (© Melting Spot/Alamy Stock Photo)

Sunset in Val Gardena in the Dolomites of South Tyrol, Italy (© Marco Capellari/Getty Images)

A Brandt's cormorant hunts for a meal in a school of Pacific mackerel beneath an oil rig off the coast of Los Angeles, California, USA (© Alex Mustard/Minden Pictures)

Colourful stained-glass window at the CST railway station (earlier Victoria Terminus), Mumbai (© Natalie Solveland/Alamy Stock Photo)

Backcountry adventurer Alex Peterson speed riding on the south side of Mount Hood, Oregon, USA (© Richard Hallman/DEEPOL by plainpicture)

Burrowing parrots in Las Lajas, Argentina (© Cagan Hakki Sekercioglu/Getty Images)

Eurasian red squirrel in the Cairngorms, Scottish Highlands, Scotland (© Images from BarbAnna/Getty Images)

Northern lights near Whitehorse in Yukon, Canada (© Design Pics/Danita Delimont)

Zebras and wildebeests in the Serengeti National Park in Tanzania (© Raffi Maghdessian/Cavan Images)

Sunlit ridges against volcanic scree on Eyjafjallajökull, a volcano in Iceland (© Erlend Haarberg/Minden Pictures)

The Chinese New Year celebration in Xi'an, China (© Aleksandar Plavevski/Shutterstock)

Military motorcycle stunt riders at Rajpath, on Republic Day 2013 (© AP Photo/Kevin Frayer)

View of New York City from the International Space Station (© NASA Photo/Alamy)

Aerial view of the glaciers and mountains of Kluane National Park and Reserve, near Haines Junction, Yukon, Canada (© Robert Postma/plainpicture)

Semuc Champey nature park in Guatemala (© Joel Sharpe/Getty Images)

Aerial view of car crossing over the frozen surface of Lake Baikal, Russia (© Amazing Aerial Agency/Offset)

A reddish egret hunts in Fort De Soto Park, Florida, USA (© Brian Lasenby/Getty Images)

Amber Fort near Jaipur, Rajasthan (© Luigi Vaccarella/Sime/eStock Photo)