Mississippi River on the border between Arkansas and Mississippi, USA (© NASA)

Ostriches in Kgalagadi Transfrontier Park, South Africa (© Tina Malfilatre/Minden Pictures)

Lençóis Maranhenses National Park, Brazil (© WIN-Initiative/Getty Images)

Lighthouse at Cape Aniva, Sakhalin, Russia (© Amazing Aerial Agency/Offset by Shutterstock)

Ostereierbaum (Easter egg tree) in Saalfeld, Germany (© Rudi Sebastian/Alamy)

Saut de Brot stone bridge, Areuse Gorge, Switzerland (© Andreas Gerth/eStock Photo)

Parthenon temple, Acropolis of Athens, Greece (© Lucky-photographer/Shutterstock)

Étretat, Normandy, France (© StevanZZ/Alamy)

Black grouse male, Kuusamo, Finland (© Oliver Smart/Alamy)

Hovenweep National Monument, Utah, USA (© Brad McGinley Photography/Getty Images)

Grizzly bear cubs in Denali National Park, Alaska, USA (© Ron Niebrugge/Alamy)

Mount Yoshino, Nara Prefecture, Japan (© Sean Pavone/iStock/Getty Images Plus)

Earth from the International Space Station (© Jeff Williams/NASA)

Wat Phra Si Sanphet, Ayutthaya, Thailand (© travelstock44/Alamy)

Carrizo Plain National Monument, California, USA (© Dennis Frates/Alamy)

Abraham Lake, Alberta, Canada (© Coolbiere/Getty Images)

Dinan, Brittany, France (© Scott Wilson/Alamy)

New River Gorge Bridge, New River Gorge National Park and Preserve, West Virginia, USA (© Entropy Workshop/iStock/Getty Images Plus)

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

Munk's pygmy devil rays, Gulf of California, Mexico (© Mark Carwardine/Minden Pictures)

Tegalalang Rice Terraces, Ubud, Bali, Indonesia (© Michele Falzone/Alamy)

Madeira, Portugal (© Hemis/Alamy)

Fairy Glen, Betws-y-Coed, Wales, United Kingdom (© Robert Harding World Imagery/Offset by Shutterstock)

Cholla Cactus Garden, Joshua Tree National Park, California, USA (© Bryan Jolley/Tandem Stills + Motion)

Adélie penguins, Antarctica (© Mike Hill/Getty Images)

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

Prairie crocus, Sandilands Provincial Forest, Manitoba, Canada (© Jaynes Gallery/Danita Delimont)

Northern gannets, Great Saltee Island, Ireland (© Danny Green/Minden Pictures)

Mockhorn Island State Wildlife Management Area, Virginia, USA (© Shane Gross/Minden Pictures)

Mont-Saint-Michel, Normandy, France (© Mathieu Rivrin/Getty Images)