Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Drivers push cars to gas station during “oil crisis”, Roslindale, Boston, Massachusetts, 1973. (Photo by Spencer Grant/Getty Images)

Amundsen-Scott South Pole Station experiences months of darkness. The sun dips below the horizon on March 21, after which follows several weeks of twilight before complete darkness results. Photo taken on June 25, 2009. (National Science Foundation/Jeremy Johnson)

A girl attends a performance hosted by the Ministry of the Interior that includes police, border guards, and rescuers celebrating International Children's Day in Kyiv, Ukraine on June 1, 2021. (Photo by Gleb Garanich/Reuters)

The civilised world lies on its knees, a sickness wracking its body. The affliction causes a necrotising of tissues so perfectly uniform in distribution that victims take on the appearance of corpses long before death occurs due to organ failure or secondary infections. ...

This photographer has made it her mission to change people’s perception of pigeons – focusing on some of the most beautiful of the more than 300 species found globally. Rather than focus on the gray, nondescript birds people usually associate with the term “pigeon”, Leila Jeffreys has instead decided to snap the more vibrant varieties. Whether it be the wompoo pigeon, with its deep purple breast and green wings, or the rose-crowned fruit dove, with its pink head, Jeffreys, 46, gives the birds the same attention she would give a human model. (Photo by Leila Jefferies/Caters News Agency)

Two carnival revellers masquerade as Leonardo da Vinci's painting “Mona Lisa” pose in St. Mark's Square in Venice, Italy, Sunday, January 31, 2016. Carnival-goers in Venice are being asked by police to momentarily lift their masks as part of new anti-terrorism measures for the annual festivities. (Photo by Domenico Stinellis/AP Photo)