Sunset from Olmsted Point, Yosemite National Park, California, United States (© Robb Hirsch/Tandem Stills + Motion)

Chattooga River in the Appalachian Mountains, North Carolina, United States (© mtilghma/Getty Images)

Brown bear in Silver Salmon Creek, Lake Clark National Park and Preserve, Alaska, United States (© Danny Green/Nature Picture Library)

Château de Castelnaud overlooking the river Dordogne, France (© garethkirklandphotogrphy/Getty Images)

Adélie penguins, Antarctica (© Otto Plantema/Minden Pictures)

Danxia landform, Zhangye National Geopark, Gansu, China (© Weiquan Lin/Getty Images)

Moss-covered rocks in Puzzlewood, Forest of Dean, Gloucestershire, England (© Fulcanelli_AOS/Getty Images)

Octopus in defensive posture, Mayotte, Indian Ocean (© Gabriel Barathieu/Minden Pictures)

View of the Sanguinaires Islands from Corsica, France (© Francesco Riccardo Iacomino/Getty Images)

Double-crested cormorants over Monterey Bay, California, United States (© Hiroya Minakuchi/Minden Pictures)

Glade Creek Grist Mill, Babcock State Park, West Virginia, United States (© dszc/Getty Images)

Mumbles Pier, Swansea, Wales (© Helen Hotson/Shutterstock)

Plitvice Lakes National Park, Croatia (© Jan Wlodarczyk/Alamy)

Ammonite fossils from the Jurassic Period (© J Nemchinova/Getty Images)

Horseshoe Falls illuminated at night in Niagara Falls, Ontario, Canada (© Jianmei Wang/Getty Images)

Mount Sneffels in the San Juan Mountains near Ridgway, Colorado, United States (© lightphoto/Getty Images)

Medieval Aqueduct, Perugia, Italy (© Marco Saracco/Getty Images)

Dolbadarn Castle, Llanberis, Eryri National Park (Snowdonia), Wales (© joe daniel price/Getty Images)

Grand Canal in Venice, Italy (© Juan Romero/Cavan Images)

Brown-throated sloth, Puerto Viejo de Talamanca, Costa Rica (© Suzi Eszterhas/Minden Pictures)

Nguyen Hoang Bridge over the Perfume River, Hue, Vietnam (© VU PHAM VAN/Getty Images)

Autumn in Naejangsan National Park, South Korea (© Twenty47studio/Getty Images)

Two grey wolves, Yellowstone National Park, Wyoming, United States (© John Morrison/Getty Images)

Green-headed tanager (© Juan Carlos Vindas/Getty Images)

Maligne Lake, Jasper National Park, Alberta, Canada (© Andrey Popov/Getty Images)