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

Conwy Castle illuminated at night, Conwy (© Jon Arnold/DanitaDelimont.com)

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

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

Divers at El Pit Cenote, located in Dos Ojos Natural Park, Quintana Roo, Mexico (© Christia Vizl/Tandem Stills + Motion)

Fairy chimneys and cave dwellings in Uçhisar, Cappadocia, Turkey (© Ivan Kmit/Alamy)

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

The catalogue and enquiries stall at the Women's Exhibition, London, May 1909. (© Museum of London/Heritage Images/Getty Images)

Flowing clouds over the Atlantic Ocean and Tenerife mountains, Canary Islands, Spain (© MikeMareen/iStock/Getty Images Plus)

Bird's-eye view of Bronte Baths ocean pool outside Sydney, Australia (© Shay Cooper/Media Drum World/Cavan Images)

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

Aerial view of Superkilen Park in Norrebro district in Copenhagen, Denmark (© Oliver Förstner/Alamy)

Loughrigg Tarn sunrise, Ambleside, Lake District (© John Finney photography/Getty Images)

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

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

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

Mother owl dotes on her newborn son at their farmyard abode (© Cavan Images/Media Drum World/Laura Dyer)

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

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

The Radcliffe Camera, Oxford for Tolkien Reading Day (© Joe Daniel Price/Getty Images)

Aerial view of the Big Sur coastline near Monterey, California, USA (© Blue Planet Archive/Alamy)

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

Orgues d'Ille-sur-Têt, Eastern Pyrenees, France (© SFL Choice/Alamy Stock Photo)

Leopard snoozing in a tree in Namibia (© M. Watsonantheo/SuperStock)

The Twist bridges the Randselva River, at the Kistefos Museum's sculpture park in Norway (© Laurian Ghinitoiu)

Ruffed grouse in Algonquin Provincial Park, Ontario, Canada (© Jim Cumming/Getty Images)