On the western side of Mount Hood lies the longest glacier cave system in the contiguous United States. In 2012, these caves were mapped to a combined length of 7,166.8 feet by cave explorers Brent McGregor and Eddy Cartaya. Currently, the total passage length is hundreds of feet less. Glaciers are frozen rivers; they are always moving and changing... (Photo and caption by Josh Hydeman)

A girl reacts as she receives polio vaccine drops during a house-to-house vaccination campaign in Yemen's capital Sanaa, November 10, 2015. (Photo by Khaled Abdullah/Reuters)

Mark Wagner, the collage artist, challenges viewers to examine their relationship with money and the capitalist society in which we live. Photo: “Way of the Dinosaur”, cut one-dollar bills. (Photo by Mark Wagner)

A donkey carrying sacks of coal walks through the narrow tunnels of a coal mine, in Choa Saidan Shah in Punjab province April 29, 2014. Coal miners in Chao Saidan Shah use donkeys to transport coal from the depths of the mines to the surface. (Photo by Sara Farid/Reuters)

A relic hunter dubbed “Indiana Bones” has lifted the lid on a macabre collection of 400-year-old jewel-encrusted skeletons unearthed in churches across Europe. Art historian Paul Koudounaris has hunted down and photographed dozens of gruesome skeletons in some of the world's most secretive religious establishments. Photo: Albertus in the church of St George in Burgrain, Germany. Incredibly, some of the skeletons, which took up to five years to decorate, were even found hidden away in lock-ups and containers. (Photo by Paul Koudounaris/BNPS)

Hisakata Hiroyuki, a talented photographer from Japan, has managed to snap a group of mortal tomcats in a variety of high-flying kung fu poses. Using his own rapid-fire reactions, he photographs the lovable cats flying through the air, their legs and paws outstretched, like something out of an action movie. (Photo by Hisakata Hiroyuki/Caters News Agency)

American singer-songwriter Olivia Rodrigo accepts the Grammy award for Best Pop Vocal Album for “Sour” during the 64th Annual Grammy Awards show in Las Vegas, Nevada, U.S., April 3, 2022. (Photo by Mario Anzuoni/Reuters)

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)