In this photo taken Thursday January 17, 2013, sled dogs Poncho, left, and his blind brother Gonzo are hooked up for a run at the Muddy Paw Sled Dog Kennel, in Jefferson, N.H. Poncho has taken to helping his blind brother on regular runs. (Photo by Jim Cole/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)

Women walk past a pile of rubbish bags on a street during a strike by garbage collectors demanding delayed salaries in Sanaa, Yemen May 8, 2017. (Photo by Khaled Abdullah/Reuters)

People take part in a military exercise for civilians conducted by veterans of the Ukrainian National Guard Azov battalion, amid threat of Russian invasion, in Kyiv, Ukraine on January 30, 2022. (Photo by Gleb Garanich/Reuters)

A dog named Luna high-fives a person in the Angelino Heights neighborhood of Los Angeles, California, U.S., August 26, 2022. (Photo by Mario Anzuoni/Reuters)

Yang Shiguang, 77, performs stunts at a park in Xi'an, Shaanxi province, September 3, 2013. Yang has been a member of a stunt performance club since 2007, after retiring from a research institution. (Photo by Reuters/China Daily)

A merino lamb attempts to jump out of its enclosure to find its mother shortly before feeding time at the Educational and Reserach Station for Animal Breeding (Lehr- und Versuchsanstalt fuer Tierzucht und Tierhaltung, or LVAT) in Brandenburg state on January 27, 2012 in Gross Kreutz, Germany. Hundreds of lambs have been born at the LVAT in recent weeks in the midst of the station's lambing season. Many of the lambs will be sold just before Easter, when they will have grown to a weight of over 40kg, as lamb is the traditional German Easter meal. (Photo by Sean Gallup/Getty Images)