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)

Sri Lankan military personnel march during the country's 66th Independence Day celebrations in the central town of Kegalle, about 40 kms from the capital Colombo on February 4, 2014. Sri Lanka cemmemorates its independence from British rule on February 4, 1948. (Photo by Ishara S. Kodikara/AFP Photo)

The lightest material ever made has been produced by a team of scientists in China, a Chinese university announced.

A couple watch the sunrise in front of the Mediterranean Sea in Barcelona, Spain, Sunday, January 24, 2021. (Photo by Emilio Morenatti/AP Photo)

Yi Arias, a CORE crew member in an upbeat mood at COVID-19 mass-vaccination of healthcare workers taking place at Dodger Stadium in Los Angeles, California, U.S., January 15, 2021 (Photo by Irfan Khan/Pool via Reuters)

Children run next to a paraglider wearing Santa Claus costume landing to deliver gifts to refugee children from Karabakh region, near the village of Akunk, outside Yerevan, on December 26, 2023, as part of “ParaSanta”, an event organised by the Armenian Paragliding Club. (Photo by Karen Minasyan/AFP Photo)

Nigel Cox and Kevin Jay paint with light using fibre optic whips on the beach at Clacton-on-Sea in Essex, United Kingdom on July 25, 2023 with a superhero fighting theme. (Photo by Kevin Jay/Picture Exclusive)

The Breitling DC-3, HB-IRJ, plane fly escorted by Italian Air Force's aerobatic demonstration team, the Frecce Tricolori, during the last stage of its world tour two days ahead of the International Sion Air Show, in Sion, Switzerland, 13 September 2017. From March to September 2017, the Breitling DC-3 from 1940 has done a grand world tour in several stages, over 28 countries and flies 50000km, an amazing accomplishment for this legendary plane that will be celebrating its 77th birthday. (Photo by Christian Merz/EPA/EFE)