'Greetings from Giza,' an installation by the artist JR, Cairo, Egypt (© Ammar ABD RABBO/Abaca Press/Alamy)

Whangārei Falls near the city of Whangārei, North Island, New Zealand (© Nathan Kavumbura/Getty Images)

Cherry blossoms at Lake Tai at Wuxi, China (© Eric Yang/Getty Images)

The Kjeragbolten boulder on the mountain Kjerag in Rogaland county, Norway (© Angel FAyE/Getty Images)

Goðafoss waterfall under the northern lights, Iceland (© Anton Petrus/Getty Images)

Crested caracara birds courting in Texas (© Alan Murphy/Minden Pictures)

Old town of Málaga, Spain (© Sean Pavone Photo/Getty Images)

Coast near Ponta Delgada, Madeira, Portugal (© Jan Wlodarczyk/Alamy)

Arvada Skatepark, Arvada, Colorado (© Jon Paciaroni/Getty Images)

Caracal cubs (© Marion Vollborn/Minden Pictures)

Fiddlehead fern fronds in Quebec, Canada (© Marianna Armata/Getty Images)

Waning gibbous moon above the Earth's horizon, photographed from the International Space Station (© NASA)

Mitsumata (aka paperbush) in a forest in Japan (© nattya3714/Getty Images)

Horseshoe Bend, Arizona (© Michael Dunn/Getty Images)

Aerial view of Grand Prismatic Spring, Yellowstone National Park, Wyoming (© AirPano LLC/Amazing Aerial Agency)

The blue eggs of an American robin in New Jersey (© Mira/Alamy)

Square Tower House in Mesa Verde National Park, Colorado (© lightphoto/Getty Images)

Plitvice Lakes National Park, Croatia (© Janne Kahila/Getty Images)

Mute swan chicks shelter under mom's tail feathers, Massapequa Preserve, Long Island, New York (© Vicki Jauron/Getty Images)

Sheep graze along a road, Iceland (© Matthew Kuhns/Tandem Stills + Motion)

Small lake in Karula National Park, Valgamaa County, Estonia (© Sven Zacek/Minden Pictures)

Tianjin Binhai New Area Library in Tianjin, China (© Imaginechina Limited/Alamy)

Milky Way rising above Half Dome in Yosemite National Park, California (© Cory Marshall/Tandem Stills + Motion)

Three king penguins on the shore of St. Andrew's Bay, South Georgia Island (© Paul Souders/Getty Images)

Central Park, New York City (© Tony Shi Photography/Getty Images)

Midnight sun in Svalbard, Norway (© Nature Picture Library/Alamy)

Fox kits practice their hunting skills, Quebec, Canada (© Vlad Kamenski/Shutterstock)

A young coast redwood sprouting out of an old log in Prairie Creek Redwoods State Park, California (© Hutch Axilrod/Getty Images)

The North Beach Jazz Mural created by Bay Area artist Bill Weber in San Francisco (© Kosso/Getty Images)