Travertine terraces of Pamukkale, Turkey (© bybostanci/Getty Images)

Travertine terraces, Pamukkale, Turkey (© bybostanci/Getty Images)

Wadi Rum, Jordan (© Thomas Coex/AFP via Getty Images)

Tree in blue agave field in the tequila producing region near Atotonilco, Jalisco, Mexico (© Brian Overcast/Alamy)

A path winding through a forest of bluebells in Hertfordshire (© JayKay57/Getty Images)

Swedish antenna at La Silla ESO Observatory, Chile (© Alberto Ghizzi Panizza/Getty Images)

Ancient theatre of Taormina in Sicily, Italy (© Antonino Bartuccio/eStock Photo)

View of Göreme from an observation deck, Göreme National Park, Cappadocia, Turkey (© Anton Petrus/Getty Images)

Grey seal with laughing expression on a stony beach in Norfolk, England (© the_guitar_mann/iStock/Getty Images Plus/Getty Images)

The village of Oia on the island of Santorini, Greece (© Zebra-Studio/Shutterstock)

Nurses serving with the American Red Cross in Paris, France, in May 1919 (© Universal History Archive/Universal Images Group via Getty Images)

Masai giraffe in Maasai Mara, Kenya (© Andy Rouse/Minden Pictures)

Masai giraffe, Maasai Mara, Kenya (© Andy Rouse/Minden Pictures)

Panoramic view of the Bernina Range with blood moon, Eastern Alps, Switzerland (© Bernd Zoller/Shutterstock)

Burrowing owl chicks near Pawnee National Grassland in Colorado, USA (© Roberta Olenick/Alamy)

Salt ponds of Maras in Peru's Sacred Valley of the Incas (© Fotofeeling/Westend61 on Offset/Shutterstock)

Museum at Prairiefire, Overland Park, Kansas, USA (© Bernard P. Friel/Universal Images Group via Getty Images)

Misty sunrise on the River Brathay in the Lake District, Cumbria (© fstopphotography/Getty Images)

Honey bee flying over crocuses in the Tatra Mountains, Poland (© Mirek Kijewski/Getty Images)

Albion Falls, Hamilton, Ontario, Canada (© Alexander Sviridov/Shutterstock)

A Burchell's zebra and a cattle egret at the Rietvlei Nature Reserve in South Africa (© Richard Du Toit/Minden Pictures)

Florida red-bellied turtle in Rainbow Springs, Rainbow Springs State Park, Florida, USA (© Michel Roggo/Minden Pictures)

Kornati National Park, Croatia (© Anton Petrus/Getty Images)

Alhambra in Granada, Andalucia, Spain (© Armand Tamboly/Getty Images)

Alhambra, Granada, Andalucia, Spain (© Armand Tamboly/Getty Images)

Golden Gate Bridge and Marin Headlands in San Francisco, California, USA (© Jeff Lewis/Tandem Stills + Motion)

Bungle Bungle Range in Purnululu National Park, Australia (© Francesco Riccardo Iacomino/Getty Images)

Hyalite Creek in the Custer Gallatin National Forest, Montana, USA (© Jared Lloyd/Getty Images)

Hanging bridge in Monteverde Cloud Forest, Costa Rica (© Dmitriy Burlakov/Getty Images)

Coral reef in Marovo Lagoon in the Solomon Islands (© WaterFrame/Alamy)