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)

Delphina Bianchi, 10, sits on the bed of a truck carrying giant pumpkins from her grandfather's John Muller's farm at the Annual Safeway World Championship Pumpkin Weigh-Off Monday, October 12, 2015, in Half Moon Bay, Calif. (Photo by Marcio Jose Sanchez/AP Photo)

John Hawkley and his wife Patty Hawkley stand next to their 2,058 pound pumpkin and celebrate after winning the 41st Annual Safeway World Championship Pumpkin Weigh-Off on October 13, 2014 in Half Moon Bay, California. John Hawkley of Napa, California won the 41st Annual Safeway World Championship Pumpkin Weigh-Off and broke a state record with his gigantic pumpkin weighing in at 2,085 pounds. Hawkley took home a cash prize of $12,510, or $6.00 a pound. (Photo by Justin Sullivan/Getty Images)

In time for Halloween the Maniac Pumpkin Carvers, creative art studio, held the Cotton Candy Machine workshop in Brooklyn, N.Y., demonstrating techniques and tools to create intricate pumpkin art. Maniac Pumpkin Carvers, which focuses on elevating the art of pumpkin carving, were a past winner of the Food Network's Halloween Wars. Their work has been displayed at MOMA, the Whitney Museum and Yankee Stadium. Here: A Tara Bonethrower pumpkin created by the Maniac Pumpkin Carvers at Cotton Candy Machine in Brooklyn, N.Y. on October 18, 2014. (Photo by Siemond Chan/Yahoo Finance)

Nothing says Halloween like a jack-o'-lantern, but these professional carvings will blow your neighborhood pumpkin out of the water. (Photo by Frank C. Grace/Courtesy Jack-O-Lantern Spectacular)

Alfred the frog looks almost as scary as the pumpkin he is perched on at London Zoo 26 October 2011. Keepers at the zoo have joined in the Halloween tradition by supplying pumpkin lunches to some of their animals, including the giant waxy monkey frog. However Alfred is not quite the giant figure his species name suggests – he actually measures up at around 4 inches (10 centimeters). (Photo by EPA/Zoological Society of London)

Five hundred replicas of the Stormtrooper characters from "Star Wars" are placed on the steps at the Juyongguan section of the Great Wall of China during a promotional event for "Star Wars: The Force Awakens" film, on the outskirts of Beijing, China, October 20, 2015. (Photo by Jason Lee/Reuters)

A reef shell lies on a beach as the sun sets on Lady Elliot Island located north-east of the town of Bundaberg in Queensland, Australia, June 10, 2015. UNESCO World Heritage delegates recently snorkelled on Australia’s Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was “poor”. (Photo by David Gray/Reuters)