Medieval city walls, Ávila, Spain (© Alberto Loyo/Getty Images)

Mer de Glace on the Mont Blanc massif, Chamonix, France (© Hagenmuller Jean-François/Hemis/Alamy)

Beech trees and wild anemones, Jutland, Denmark (© Nick Brundle Photography/Getty Images)

A rainbow in At-Bashy District, Kakshaal Too mountains, Naryn Region, Kyrgyzstan (© Emad aljumah/Getty Images)

Lechwe herd crossing marshy plain of Okavango Delta, Botswana (© Ibrahim Suha Derbent/Getty Images)

The Bahamas photographed from the International Space Station (© NASA)

Himeji Castle, Himeji, Hyōgo Prefecture, Japan (© Julian Elliott Photography/Getty Images)

North American beaver in a pond near Wonder Lake, Denali National Park, Alaska (© Paul Souders/Getty Images)

European hedgehog in a garden with dandelions, Bad Driburg, Germany (© Oksana Schmidt/Getty Images)

Tulip fields in spring, Skagit Valley, Washington, USA (© Claudia Cooper/Getty Images)

Burrowing owl chicks near a burrow, Wyoming, USA (© Danita Delimont/Getty Images)

Aerial view of Churun-Meru (Dragon) waterfall, Venezuela (© AirPano LLC/Amazing Aerial Agency)

Evening light over North Window with Turret Arch in the distance, Arches National Park, Utah, USA (© Anthony Heflin/Shutterstock)

Apple trees in spring, Germany (© Smileus/Getty Images)

Sunset on Bowling Ball Beach, Mendocino County, California, USA (© Melo Qiao/Getty Images)

Château de Chambord, Centre-Val de Loire, France (© Susanne Kremer/eStock Photo)

Union Square in lower Manhattan at twilight, New York, USA (© Sean Pavone/Getty Images)

American black bear cub in spring, Shenandoah National Park, Virginia, USA (© Scott Suriano/Getty Images)

The Ring of Brodgar, Orkney, Scotland (© Paul Williams - FunkyStock/Getty Images)

Grand Prismatic Spring at sunrise, Yellowstone National Park, Wyoming, USA (© XIN WANG/Getty Images)

Sparks Lane in Cades Cove, Great Smoky Mountains National Park, Tennessee, USA (© Richard Bernabe/Shutterstock)

Green sea turtle, San Diego, California, USA (© Ralph Pace/Minden Pictures)

Library of Trinity College Dublin, Ireland (© Lukas Bischoff/Getty Images)

White trillium blooming in Ontario, Canada (© Jun Zhang/Getty Images)

Adélie penguins on an iceberg, Antarctica (© Patrick J. Endres/Getty Images)

Kalaloch Tree of Life, Kalaloch Beach, Olympic National Park, Washington, USA (© Abbie Warnock-Matthews/Shutterstock)

Leucistic Anna's hummingbird in the Australia Garden, UCSC Arboretum, Santa Cruz, California, USA (© yhelfman/Getty Images)

El Capitan at sunrise in Guadalupe Mountains National Park, Texas, USA (© Adam Mowery/Tandem Stills + Motion)

Fujian Tulou complex of historical and cultural heritage buildings in Fujian province, China (© Hongjie Han/Getty Images)

Cheetah in morning rain, Ndutu Plains, Ngorongoro Conservation Area, Tanzania (© Paul Souders/Getty Images)