For centuries the Highlands peoples of Papua New Guinea fought over land, women and pigs. Sorcery and battle skills could elevate a clan to Bigmanship, where the bigger the “presentation”, the bigger the man. Clans therefore would paint their bodies and create fearsome masks as part of their psy. Here: These are the terrifying tribe of “mudmen” from a remote part of Papua New Guinea. (Photo by Jeremy Hunter/Exclusivepix Media)

A cloud of black smoke billows out the exhaust pipe of John Robertson's diesel dragster as he runs down the track during the 2015 NHRA Kansas Nationals, Friday, May 22, 2015, at Heartland Park in Topeka, Kan. (Photo by Chris Neal/The Topeka Capital-Journal via AP Photo)

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)

Moruti Mthalane of South Africa is punched by Masayuki Kuroda of Japan during their IBF flyweight title boxing bout in Tokyo on May 13, 2019. (Photo by Charly Triballeau/AFP Photo)

David Reutimann, driver of the #00 Aaron's Dream Machine Toyota, Brian Vickers, driver of the #83 Red Bull Toyota, and Denny Hamlin, driver of the #11 FedEx Express Toyota, collide after an incident in the NASCAR Sprint Cup Series Jeff Byrd 500 Presented By Food City at Bristol Motor Speedway on March 20, 2011 in Bristol, Tennessee.

A two-horse team street cleaner, with sprayer, squeegee, and roller at rear. New York, between ca. 1910 and ca. 1915. (Photo by NYC Municipal Archives)