Palermo skyline at dusk, Sicily, Italy (© Sean Pavone/Getty Images)

Highway through Xitai Jinaier Lake, Qinghai Province, China (© Kaicheng Xu/Getty Images)

Cyclist in Bardenas Reales Natural Park and Biosphere Reserve, Navarra, Spain (© Artur Debat/Getty Images)

Snowy egret preening, central Florida, United States (© Donald M. Jones/Minden Pictures)

View from Skierffe Mountain over the Rapadalen river delta, Sarek National Park, Laponia, Lapland, Sweden (© Robert Haasmann/Getty Images)

Ruins of Dunseverick Castle, County Antrim, Northern Ireland (© Krzysztof Rogalski/Getty Images)

Lion's mane jellyfish swimming in the ocean (© Alexander Semenov Images/Shutterstock)

Vernazza, Cinque Terre, Liguria, Italy (© Kelly Cheng/Getty Images)

Hnausapollur volcanic crater lake, Fjallabak Nature Reserve, Landmannalaugar, Iceland (© Juan Maria Coy Vergara/Getty Images)

Limpets exposed at low tide on the coast of Praia da Ursa, Portugal (© Theo Bosboom/Nature Picture Library)

European bee-eater in Sierra de Grazalema Natural Park, Cádiz, Spain (© Andres M. Dominguez/Nature Picture Library)

Sunset in Badlands National Park, South Dakota, United States (© Troy Harrison/Getty Images)

Mallard duck (© Philippe Paternolli/Getty Images)

Great Smoky Mountains National Park, Tennessee, United States (© Mint Images/Getty Images)

Hawksbill sea turtle pair near Seven Mile Beach, Grand Cayman, Cayman Islands (© Alex Mustard/Nature Picture Library)

Tremola Road on the Saint Gotthard Pass in Airolo, Switzerland (© Sandro Bisaro/Getty Images)

Aerial view of the ruins of Sacsayhuamán, Cusco, Peru (© Creative-Family/Getty Images Plus)

La Rocchetta Lighthouse, Piombino, Italy (© StevanZZ/Getty Images)

Arched iceberg floating off the western Antarctic Peninsula, Southern Ocean (© Steven Kazlowski/Nature Picture Library)

Red maple leaf, symbol of Canada (© namaki/Getty Images)