A woman stands in front of graffiti depicting Venezuela's late former President Hugo Chavez, right, and revolutionary hero Simon Bolivar, in downtown Caracas, Venezuela, Wednesday, October 25, 2017. (Photo by Rodrigo Abd/AP Photo)

“Red Arrows” at the 2016 royal air tattoo, RAF Fairford, UK. By Jonny Williams, finalist: action. (Photo by Jonny Williams/UK National Geographic Traveller Photography Competition 2018)

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)

In this Sunday, March 11, 2017 photo, children fight in a boxing ring in Chitungwiza, Zimbabwe. Zimbabwean boys as young as 10 hurry every weekend to a boxing ring whose nickname, Wafa Wafa, in the local Shona language suggests that whoever enters will be lucky to come out alive. (Photo by Tsvangirayi Mukwazhi/AP Photo)

A tourist struggles in the water, before standing up and wading away, after a wave strengthened by the influence of Typhoon Dujuan hit a river bank in Hangzhou, Zhejiang province September 29, 2015. (Photo by Reuters/China Daily)

Talk about being in the eye of the storm! These stunning snaps show breath-taking storms from an extraordinary up-close perspective. Taken by daredevil storm chaser Dennis Oswald, from Neuss, Germany, the amazing pictures capture spectacular storms from around the globe. Having chased storms for nearly 15 years, experienced Dennis gets right in the action to get these incredible shots. Here: scenic mothership supercell just north of Howard, Kansas. (Photo by Dennis Oswald/Caters News)

Food is placed on the tomb of pet dog Xixi at Baifu pet cemetery ahead of the Qingming Festival on the outskirts of Beijing, China March 26, 2016. The Chinese characters on the gravestone read: “Mommy's only good son”. (Photo by Jason Lee/Reuters)

A young Afghan vendor waits for customers to buy sheep's heads at a roadside stall at the busy market in Kabul on November 29, 2015. (Photo by Wakil Kohsar/AFP Photo)