London Millennium Bridge with St. Paul's Cathedral in the background, London, England (© Scott Baldock/Getty Images)

Great Barrier Reef, Queensland, Australia (© AWL Images/Danita Delimont)

Two mountain bike riders make their way down the Shafer Trail switchbacks on White Rim Road in Canyonlands National Park, Utah (© Grant Ordelheide/Tandem Stills + Motion)

View of a waterfall at Mystic Beach in Juan de Fuca Provincial Park, B.C. during dusk (© DEEPOL/Plainpicture)

Synchronous fireflies illuminate the forests of Great Smoky Mountains National Park, Tennessee, USA (© Floris van Breugel/Minden Pictures)

Walter's Wiggles trail in Zion National Park, Utah, USA (© Dennis Frates/Alamy)

Hermitage of La Pertusa, Lleida province, Spain (© bbsferrari/Getty Images)

Galápagos sea lion off the shore of Fernandina Island, Galápagos Islands, Ecuador (© Tui De Roy/Minden Pictures)

Baron Lake in the Sawtooth Wilderness in Idaho, USA (© Patrick Brandenburg/Tandem Stills + Motion)

Griboyedov Canal and the Church of the Savior on Spilled Blood in Saint Petersburg, Russia (© Tomas Sereda/Getty Images)

Beaver Falls on Havasu Creek in the Grand Canyon, Arizona, USA (© Edwin Verin/Alamy)

The Dourbie Gorge Corps Mill and adjoining bridge in Grands Causses Natural Regional Park, France (© Hemis/Alamy)

The Dourbie Gorge Corps Mill and adjoining bridge in Grands Causses Regional Nature Park, France (© Hemis/Alamy)

Melaleuca trees in a stream after cyclonic rainfall, Western Australia (© Ted Mead/Getty Images)

St. Stephen's Green in Dublin, Ireland (© L_E/Shutterstock)

Eibsee lake at the base of Zugspitze mountain, Bavaria, Germany (© Marc Hohenleitner/Huber/eStock Photo)

Beaver Falls on Havasu Creek in the Grand Canyon, Arizona (© Edwin Verin/Alamy)

Midsummer light captured at a lake near the city of Örebro, Sweden (© Anders Jorulf/Getty Images)

Midsummer light captured at a lake near the city of Örebro, Sweden (© Anders Jorulf/Getty Images)

The Bojo River in Cebu, Philippines (© Amazing Aerial Agency/Offset by Shutterstock)

Cattleman’s hut at Dinner Plain, Victoria (© Viewhillphoto/iStock/Getty Images Plus)

Bull Point in Devon, England (© Robert Harding World Imagery/Offset by Shutterstock)

Pont Fawr, a stone arch bridge in Llanrwst, Wales, UK (© Pajor Pawel/Shutterstock)

German Navy tall ship Gorch Fock in waters close to Reykjavík, Iceland (© DEEPOL by plainpicture/Henn Photography)

German navy tall ship Gorch Fock in waters close to Reykjavík, Iceland (© DEEPOL by plainpicture/Henn Photography)

The Sanctuary of Madonna della Corona in Italy (© Volodymyr Kalyniuk/Alamy)

The Empire State Building lit up in honour of Pride Weekend in 2014, New York City, USA (© C. Taylor Crothers/Offset by Shutterstock)

Goats in an argan tree near Essaouira, Morocco (© Nizz/Shutterstock)

Frozen tarn, Cradle Mountain, Tasmania (© TED MEAD/Getty Images)

Moraine Lake in Banff National Park, Alberta, Canada (© Schroptschop/Getty Images)