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

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

Fairy Glen, Betws-y-coed, Conwy (© Robert Harding World Imagery/Offset by Shutterstock)

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

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

Thoseghar Waterfalls in Maharashtra, India (© Sonali Kumar/iStock/Getty Images Plus)

Norcross Brook and wetlands, Maine, USA (© Aaron Black-Schmidt/Tandem Stills + Motion)

Black-tailed godwits, Netherlands (© Edward van Altena/Minden Pictures)

Sunset over Buttermere, Lake District, Cumbria (© Stewart Smith/Alamy)

Aerial view of Mainau island on Lake Constance, Germany (© Amazing Aerial Agency/Offset by Shutterstock)

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

A view across the River Shannon in Limerick, County Limerick, Ireland (© Piotr Machowczyk/Shutterstock)

A view across the River Shannon in Limerick, County Limerick, Ireland (© Piotr Machowczyk/Shutterstock)

Jagged coastal sea stacks at Mangersta, Isle of Lewis, Outer Hebrides (© Cody Duncan/Cavan Images)

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)

Ålesund, Norway (© AWL Images/Offset by Shutterstock)

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

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

Whooping cranes taking off during spring migration in South Dakota, USA (© Gerrit Vyn/Minden Pictures)

Cube houses in Rotterdam, the Netherlands (© Don Mennig/Alamy)

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

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)

Montalbano Elicona, Messina, Sicily, Italy (© Antonino Bartuccio/SOPA Collection/Offset by Shutterstock)

The total lunar eclipse of April 4, 2015, photographed over Monument Valley, Utah (© Alan Dyer/Alamy)

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

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

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

View along the beach to Eastbourne Pier, Eastbourne, East Sussex. (© Robert Harding World Imagery/Offset by Shutterstock)

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