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 woman poses by “Leaf Spirit” by Simon Gudgeon at the FORM 24 show at Sculpture by the Lakes, on April 02, 2024 in Dorchester, England. The award-winning sculpture show runs from April 2 to June 1, with works by more than 35 leading contemporary sculptors exhibited throughout 26-acres of lakes, rivers, gardens, and woodlands as well as in the Gallery and The Retreat. FORM includes a series of talks and events to accompany the exhibition, including “Meet the Artist” Q&A sessions with exhibiting sculptors, workshops and demonstrations. (Photo by Finnbarr Webster/Getty Images)

These beautiful shots may look like works of modern art – but they are actually close-ups of chemical reactions. The works were snapped with the help of a group of scientists from the University of Science and Technology of China (USTC) in Anhui, China. Here: Zinc reacting with lead nitrate in a soft gel to form lead crystals. (Photo by Yan Liang/Caters News)

A remote-controlled plane in the form of a witch flies over a neighborhood as the sun sets during Halloween in Encinitas, California, U.S. October 31, 2016. (Photo by Mike Blake/Reuters)

People fall down as they try to form a human pyramid to break the “Dahi handi”, an earthen pot filled with curd, an integral part of celebrations to mark Janmashtami in Mumbai, India, Monday, August 18, 2014. Hindu devotees take part in the celebration in which an earthen pot is suspended high above the ground and groups of young men and children form a human pyramid to reach the pot and break it. The festival celebrates the birth of Hindu god Lord Krishna, one of the most popular gods in Hinduism. (Photo by Rafiq Maqbool/AP Photo)

Layers of breathtaking colour streak the rolling hills of this vast desert, making the landscape appear as though it has been tie-dyed. The natural phenomenon, nicknamed the “Painted Desert”, was formed when the area was once a river floodplain. Each colour corresponds to a different underground geological feature – rocks which have seemingly dyed the layers of earth above. Formed from volcanic activity, the hills at the John Day Fossil Beds National Monument in East Central Oregon, USA, are almost bursting with colour. Pictured: The colourful hills at the John Day Fossil Beds National Monument in East Central Oregon, USA. (Photo by Mark Brodkin/Solent News/SIPA Press)

In this January 27, 2014 photo, snow rollers dot a lot at the northwest corner of Olive and North Main streets in Akron, Ohio. The snow balls are formed naturally when high winds push snow across a hill. (Photo by Michael Chritton/AP Photo/Akron Beacon Journal)

Men carry a dog, wearing a costume and seated on a stool, as a form of respect as they believe that dogs found water for their ancestors, during a local festival for the Miao ethnic minority in Jianhe county, Guizhou Province, China, August 14, 2016. (Photo by Reuters/China Daily)