Amalgamated Clothing Workers of America in a Labor Day parade, May 1915, Chicago (© Chicago Sun-Times/Chicago Daily News collection/Chicago History Museum/Getty Images)

Camel thorn trees, Deadvlei, Namib-Naukluft Park, Namibia (© Inge Johnsson/Alamy)

Boundary Waters Canoe Area Wilderness, Minnesota (© s.tomas/Shutterstock)

Grizzly bears wrestling, Katmai National Park and Preserve, Alaska (© Cavan Images/Adobe Stock)

Pacific Park at Santa Monica State Beach, California (© EXTREME-PHOTOGRAPHER/Getty Images)

Rufous hummingbird, Golden Gate Park, San Francisco, California (© jeremyborkat/Getty Images)

Library@orchard, Singapore (© Darwin Fan/Getty Images)

A female Eurasian red squirrel carrying moss, Switzerland (© Jean-Luc and Francoise Ziegler/Minden Pictures)

Hay bales, North Yorkshire, England (© Nick Brundle Photography/Getty Images)

Statue of Liberty and Lower Manhattan, New York City (© Tetra Images/Getty Images)

Spinner dolphin pod in the Red Sea, Marsa Alam, Egypt (© Franco Banfi/Nature Picture Library)

Chimney Rock, Point Reyes National Seashore, California (© Enrique Aguirre Aves/Getty Images)

A waterfall in Olympic National Park, Washington (© Chris Moore/TANDEM Stills + Motion)

Latino Cultural Center designed by Ricardo Legorreta, Dallas, Texas (© Ken Hurst/Alamy)

Nighttime view of the Gulf Coast states from 225 miles above Earth (© Stocktrek Images/Getty Images)

Young bull moose in Denali National Park, Alaska (© Grant Ordelheide/TANDEM Stills + Motion)

Serpentine stairs of Dunquin Pier, County Kerry, Ireland (© Hugh O'Connor/Getty Images)

Thousand Islands region, St. Lawrence River, US-Canada border (© benedek/Getty Images)

Swing carousel at Oktoberfest, Munich, Germany (© LOOK-foto/Alamy)

Sea otters, Prince William Sound, Alaska (© Gerald Corsi/Getty Images)

Aspen trees during fall, Fishlake National Forest, Utah (© Danita Delimont/Getty Images)

Keel-billed toucan in Costa Rica (© Juan Carlos Vindas/Getty Images)

Devils Tower National Monument, Wyoming (© Laura Hedien/Getty Images)

Chittorgarh Fort, Rajasthan, India (© chetansoni/Shutterstock)

Least chipmunk, Kootenai National Forest, Montana (© Donald M. Jones/Minden Pictures)

Tank Lakes, Alpine Lakes Wilderness, Washington (© Austin Trigg/TANDEM Stills + Motion)

Town of Pienza in Tuscany, Italy (© zpagistock/Getty Images)

The Rainbow Houses of Houten, Netherlands (© George Pachantouris/Getty Images)

Koala in a eucalyptus tree, Great Otway National Park, Australia (© Jamie Lamb - elusive-images.co.uk/Getty Images)