Porto, Portugal (© Starcevic/Getty Images)

Polar bears at play in the Arctic (© Ondrej Prosicky/Shutterstock)

Star trails over Ardez village, Graubunden, Switzerland (© Roberto Moiola/Getty Images)

Radcliffe Camera and All Souls College, University of Oxford, England (© atiger/Shutterstock)

Bản Giốc – Detian Falls on the Quây Sơn River, Vietnam (© Shane P. White/Minden Pictures)

Plum-headed parakeet at Shimoga, Karnataka, India (© Hira Punjabi/Alamy Stock Photo)

Flooded crypt, Basilica of San Francesco, Ravenna, Italy (© Andrea Pucci/Getty Images)

Moeraki Boulders, South Island, New Zealand (© Douglas Pearson/eStock Photo)

Snow on the Great Wall, China (© View Stock/Alamy Stock Photo)

Sossusvlei sand dunes, Namib desert, Namibia (© Airpano/Amazing Aerial Agency)

Abraham Lake, Alberta, Canada (© Basic Elements Photography/Getty Images)

Heri es-Swani in Meknes, Morocco (© Calin Stan/Shutterstock)

Crescent-tail bigeye fish in the Great Barrier Reef, Australia (© Fred Bavendam/Minden Pictures)

Cottage and Tŵr Mawr lighthouse, Ynys Llanddwyn, Wales, United Kingdom (© Westend61 on Offset/Shutterstock)

Zahara de la Sierra, Cadiz, Spain (© SEN LI/Getty Images)

Pointe du Diable, Saint-Pierre, Réunion Island (© MONTICO Lionel/Alamy)

High Peaks Trail at Pinnacles National Park, San Benito County, California, USA (© yhelfman/Getty Images)

Brown pelican, San Diego, California, USA (© Arthur Morris/BIRDS AS ART/Getty Images)

Sunset at White Sands National Park, New Mexico, USA (© Image Professionals GmbH/Alamy Stock Photo)

Neptune's Grotto, Sardinia, Italy (© Carlo Murenu/Getty Images)

Looking over the Gulf of Naples towards Mount Vesuvius, Italy (© ezypix/Getty Images)

Eurasian red squirrel with toadstool (© Edwin Giesbers/Minden Pictures)

Ad-Deir, Petra, Jordan (© Punnawit Suwuttananun/Getty Images)

Deer Valley at dusk, Park City, Utah, USA (© Adventure_Photo/Getty Images)

Strokkur geyser in Iceland (© John and Tina Reid/Getty Images)

European beech forest in Belgium (© Philippe Moes/Minden Pictures)

Zoroaster Temple, Grand Canyon National Park, Arizona, USA (© Nick Lake/Tandem Stills + Motion)

Short-eared owl hunting in heavy snow (© Dilshan Muthalib/Getty Images)

Prioro, Castile and León, Spain (© Ruben Earth/Getty Images)

Roland's Breach, Ordesa y Monte Perdido National Park, Spain (© Inaki Relanzon/Nature Picture Library/Alamy Stock Photo)

Plains zebras at sunrise, Mokala National Park, South Africa (© EcoPrint/Shutterstock)