Chestnuts inside their husks (© Kai Keisuke/Shutterstock)

Polar bears in Torngat Mountains National Park, Canada (© Cavan Images/Offset by Shutterstock)

Loch Leum na Luirginn and Loch Cleat seen from the Quiraing, Isle of Skye, Scotland, UK (© Sebastian Wasek/Sime/eStock Photo)

Caribou swimming across Alaska's Kobuk River during autumn migration, USA (© Michio Hoshino/Minden Pictures)

Albarracín, Spain (© Domingo Leiva/Getty Images)

West Indian manatees in Three Sisters Springs, Crystal River National Wildlife Refuge, Florida, USA (© Norbert Probst/Getty Images)

Derwent Island on Derwentwater in the Lake District National Park, Cumbria, England (© Chris Warren/eStock Photo)

Derwent Island on Derwentwater in the Lake District National Park, Cumbria, England (© Chris Warren/eStock Photo)

Badlands National Park, South Dakota, USA (© Dennis Frates/Alamy)

Poppies projected on the Sydney Opera House sails to mark Remembrance Day (© James D. Morgan/Getty Images)

The hills of Barolo vineyards in Piedmont, Italy (© Marco Arduino/eStock Photo)

Ravens in a snowstorm near Kuhmo, Finland (© Frans Lemmens/Alamy)

Oil lamps being arranged on rangoli during Diwali (© Subir Basak/Getty Images)

Lupins on the shores of Lake Tekapo in New Zealand (© Stanislav Kachyna/Shutterstock)

The interior of the Abu Simbel Great Temple in Egypt (© George Steinmetz/Getty Images)

The interior of the Abu Simbel Great Temple in Egypt (© George Steinmetz/Getty Images)

Inukshuk silhouetted against the Northern Lights in Barren Lands, Northwest Territories, Canada (© Mark Duffy/Alamy)

Chestnut-mandibled toucan in nest cavity, Costa Rica (© Greg Basco/Minden Pictures)

Aerial view of the Aiguille du Midi in the Mont Blanc massif, France (© Amazing Aerial Agency/Offset by Shutterstock)

Nuestra Señora de la Hoz, an old monastery in the Duratón River gorge, Segovia, Castile and León, Spain (© Arco Images GmbH/Alamy)

Common cranes in the Drömling wetland in Germany (© Mike Friedrichs/Getty Images)

Old Town of Bern, Switzerland (© Simon Zenger/Alamy)

Huge waves crashing on rocks along Asilomar State Beach, Pacific Grove, California, USA (© Sheila Haddad/Danita Delimont)

A grove of American elm trees in Central Park's Mall, New York City, USA (© AWL Images/Danita Delimont)

A Siberian chipmunk on Mount Taisetsu, Hokkaido, Japan (© Ida Toshiaki/Minden Pictures)

Kalbarri National Park, Western Australia (© AWL Images/Offset by Shutterstock)

Partly snow-covered slope in Val Cervara, an old-growth beech forest, in Abruzzo, Italy (© Bruno D'Amicis/Minden Pictures)

Mount Taranaki, Egmont National Park, North Island, New Zealand (© Francesco Vaninetti/plainpicture)

Eilean Donan Castle in Scotland (© CBW/Alamy)

Aerial view of Cronulla rock pool with incoming waves, New South Wales (© ai_yoshi/iStock/Getty Images Plus)