The medieval walled town in Tossa de Mar, Catalonia, Spain (© dleiva/Alamy)

Burchell's zebra stallions, Rietvlei Nature Reserve, South Africa (© Richard Du Toit/Minden Pictures)

Wensleydale, Yorkshire Dales National Park, North Yorkshire, England (© Guy Edwardes/Minden Pictures)

Grey seal hitching over a beach in Donna Nook, North Lincolnshire, England (© Frederic Desmette/Minden Pictures)

The Great Pyramid of Cholula, in Cholula, Puebla, Mexico (© mauritius images GmbH/Alamy)

The Great Pyramid of Cholula, Puebla, Mexico (© mauritius images GmbH/Alamy)

Norcross Brook and wetlands near Moosehead Lake in Piscataquis County, Maine (© Aaron Black-Schmidt/Tandem Stills + Motion)

Norcross Brook and wetlands near Moosehead Lake in Piscataquis County, Maine (© Aaron Black-Schmidt/Tandem Stills + Motion)

Sea otter mother and newborn pup, Monterey Bay, California (© Suzi Eszterhas/Minden Pictures)

Sattais Kacheri at Amer Fort in Jaipur, India (© YURY TARANIK/Shutterstock)

Grinnell Lake, Glacier National Park, Montana (© Pung/Shutterstock)

Grinnell Lake, Glacier National Park, Montana, USA (© Pung/Shutterstock)

Shikisai no Oka flower gardens in Biei, Japan (© Tanya Jones/Shutterstock)

Amazon rainforest with fog in the morning near Alta Floresta, Mato Grosso, Brazil (© Pulsar Imagens/Alamy)

Telescopes and star trails at Paranal Observatory, Atacama Desert, Chile (© Matteo Omied/Alamy)

Aerial view of El Peñón de Guatapé, Guatapé, Antioquia, Colombia (© Amazing Aerial Agency/Offset by Shutterstock)

Gwalior Fort in Madhya Pradesh, India (© f9photos/iStock/Getty Images Plus)

Centre Pompidou Málaga in Málaga, Spain (© Wim Wiskerke/Alamy)

Fallen rhododendron petals line a trail on Grassy Ridge Bald, Pisgah National Forest, North Carolina (© aheflin/Getty Images Plus)

A bee dives into an East Indian lotus flower at Kenilworth Park and Aquatic Gardens in Washington, DC (© Linda Davidson/The Washington Post via Getty Images)

Hartland Point Lighthouse, Devon, England (© Adam Burton/Alamy Stock Photo)

The renovated Rose Main Reading Room inside the New York Public Library Main Branch, New York City (© Sascha Kilmer/Getty Images)

The Infinite Bridge, designed by Danish architects Niels Povlsgaard and Johan Gjødes, in Aarhus, Denmark (© Kosmaj/Shutterstock)

Sperm whale off the coast of Roseau, Dominica, in the Caribbean Sea (© Tony Wu/Minden Pictures)

Bodhi Tree in Bodh Gaya, India (© Rosita So Image/Getty Images)

'I Can Hear It,' an installation by artist Ivars Drulle on the beach by the villages of Middelkerke and Westende, Belgium (© Arterra Picture Library/Alamy)

Robin's nest with a brown-headed cowbird egg (© Edward Kinsman/Science Photo Library)

Alley with red walls and bamboo grove in Wuhou Temple, Chengdu, Sichuan province, China (© Eastimages/Getty Images)

California sea lion in a forest of giant kelp near the Channel Islands of California (© Nature Picture Library/Alamy)

Varandha Ghat in Maharashtra, India (© AmitRane1975/iStock/Getty Images Plus)

Aerial view of the Grotta della Poesia (Poetry's Cave) near Roca, Lecce, Italy (© Amazing Aerial Agency/Offset by Shutterstock)