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)

A worker spreads paddy crop for drying in a rice mill complex on the outskirts of Ahmedabad February 3, 2011. (Photo by Amit Dave/Reuters)

People perform during celebrations to commemorate the 70th anniversary of the establishment of the Vietnam Public Security police force at the National Convention Center in Hanoi August 18, 2015. The Vietnam Police force was founded on August 19, 1945, the day of the anti-colonial people's uprising known as the August Revolution. (Photo by Reuters/Kham)

A Thai veterinarian takes a picture of a 2-year-old orangutan during a health examination at Kao Pratubchang Conservation Centre in Ratchaburi, Thailand, August 27, 2015. Thai veterinarians from the Department of National Park Wildlife, and Plant Conservation conducted a health check of 14 orangutans for preparation for the repatriation to their country of origin, Indonesia. (Photo by Athit Perawongmetha/Reuters)

In this Thursday, August 17, 2017 photo, a troupe charges and fires their rifles during Tabourida, a traditional horse riding show also known as Fantasia, in Mansouria, near Casablanca, Morocco. Thousands gathered recently in Mansouria, a small town south of the capital Rabat, to attend one of the oldest festivals in Morocco. Nineteen horse troupes came from different parts of the kingdom to celebrate a three-day event that blends courage, skill and tradition. (Photo by Mosa'ab Elshamy/AP Photo)

Elderly women wait for customers as they sell their self-made food products at a street market, with a graffiti depicting Russian President Vladimir Putin on the wall of a house seen in the background, in the town of Kashira, outside Moscow, Russia on October 10, 2017. (Photo by Andrey Volkov/Reuters)

A mother raise her glass filled with 2017 Beaujolais Nouveau wine as she holds her child in a colored hot water “wine bath” at Hakone Kowakien Yunessun hot spring resort in Hakone, west of Tokyo, Japan, 16 November 2017, on the day of the Beaujolais Nouveau official release. With Germany and the United States, Japan is a major market for the Beaujolais Nouveau. (Photo by Franck Robichon/EPA/EFE)

An injured person is seen after an earthquake hit Port-au-Prince, Haiti, Tuesday, January 12, 2010. A 7.0-magnitude earthquake, the largest ever recorded in the area, rocked Haiti on Tuesday. (Photo by Jorge Cruz/AP Photo)