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)

Libyan leader Muammar Gaddafi attends the inauguration ceremony of Jacob Zuma on May 9, 2009 in Pretoria, South Africa. Jacob Gedleyihlekisa Zuma is South Africa's fourth President since the end of apartheid. (Photo by Foto24/Gallo Images/Getty Images)

The President tree is the name of a giant sequoia located in the Giant Forest of Sequoia National Park in the United States, east of Visalia, California. The tree is believed to be at least 3,200 years old.
The tree was named after President Warren G. Harding in 1923. Nearby trees include Chief Sequoyah, the 27th largest giant sequoia in the world, and the Congress Group, two dense stands of medium sized sequoias that represent the "House" and "Senate".

Indian Air Force soldiers toss their rifles as they perform during the full-dress rehearsal for Indian Air Force Day at the Hindon air force station on the outskirts of New Delhi October 6, 2015. (Photo by Anindito Mukherjee/Reuters)

Skeleton bodypainting in Chimbu tribe. Village Mindima, Simbu (a Highlands Region province in Papua New Guinea), September 14, 2009. (Photo by Rita Willaert; Source: Flickr)

One of ten little spotted kiwi is released on Motuihe Island, a conservation pest-free island close to Auckland, on March 21, 2009 in Auckland, New Zealand. Eventually up to 40 endangered kiwi birds will be relocated to the island. (Photo by Hannah Johnston/Getty Images)

Beekeeper and Chairman of The London Beekeepers Association John Chapple installs a new bee hive on an urban rooftop garden in Hackney on July 1, 2009 in London, England. (Photo by Dan Kitwood/Getty Images)

Entertainers from the She Huo cultural troupe rehearse for the Edinburgh Military Tattoo at Redford barracks on August 5, 2009 in Edinburgh, Scotland. (Photo by Jeff J Mitchell/Getty Images)