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 person looks at Australian artist Ron Muecks large-scale installation “Mass” which comprises more than 100 hand-cast skulls that collectively weigh approximately 5000 kilograms at an exhibition at the National Gallery of Victoria (NGV) in Melbourne on May 18, 2022. (Photo by William West/AFP Photo)

A Hindu holy man, or sadhu, smokes marijuana on a chillum (pipe) at the premises of Pashupatinath Temple during the Shivaratri festival in Kathmandu February 27, 2014. Hindu holy men from Nepal and India come to this temple to take part in the Shivaratri festival. Celebrated by Hindu devotees all over the world, Shivaratri is dedicated to Lord Shiva, and holy men mark the occasion by praying, smoking marijuana or smearing their bodies with ashes. (Photo by Navesh Chitrakar/Reuters)

Patrick Fellows #21, Allan McShane #26, Carson Edwardson #8 and Shaun Bily #23 of the Erie Otters sit on the bench during the first period of an OHL game against the Niagara IceDogs at the Meridian Centre on October 6, 2016 in St Catharines, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)

A street artist dances tango in Buenos Aires, Argentina, Tuesday, January 20, 2015. Tango is a partner dance that originated in the 1890's along the Rio de la Plata, the border between Uruguay and Argentina. UNESCO approved in 2009, a joint proposal by the two nations to include the dance in its Intangible Cultural Heritage List. (Photo by Rodrigo Abd/AP Photo)

In this May 2, 2015 photo, skywriter Nathan Hammond releases smoke as he writes messages of hope and love over New Orleans, during the New Orleans Jazz & Heritage Festival. Hammond was commissioned by local entrepreneur, Frank Scurlock, who said the messages were simply his way of reminding people that goodness can still flourish in a world that seems increasingly marred by violence. (Photo by Gerald Herbert/AP Photo)

Aerial view of tourists in life vests and rubber rafts in the Grand Canyon of western Henan, Sanmenxia, China on August 5, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

WWII veterans attend a ceremony to place tobacco pouches of soil from WWII mass graves of Red Army soldiers abroad, in the custody of the Central Armed Forces Museum in Moscow, Russia on March 6, 2020. The grave soil has been brought from Abkhazia, Germany, Kyrgyzstan, US, Ukraine, France, Estonia, Mongolia, Bulgaria, UK, Uzbekistan and South Ossetia. (Photo by Alexander Shcherbak/TASS)