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 shouts asking for help during an eviction in Rio de Janeiro, Brazil, Friday, April 11, 2014. Squatters in Rio de Janeiro are clashing with police after a Brazilian court ordered that 5,000 people be evicted from abandoned buildings of a telecommunications company. Officers have used tear gas and stun grenades to try to disperse the families. (Photo by Silvia Izquierdo/AP Photo)

A trapped car is pushed along a flooded street after typhoon Soudelor hit Fuzhou, Fujian province, China, August 9, 2015. The typhoon battered China's east coast on Sunday, killing eight people and forcing authorities to cancel hundreds of flights and evacuate more than 163,000 people. (Photo by Reuters/Stringer)

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)

These girls are scantily dressed as they head out for a night out in Portsmouth, Hampshire on September 21, 2016 in matching outfits. Thousands of Portsmouth University students enjoy freshers week. Teenagers enjoy their first taste of freedom in bars and clubs near Portsmouth Guildhall which on a midweek alcohol fuelled night of fun in the early hours of Wednesday morning much to the despair of local residents who get disturbed up to 4am when they eventually wander home. Girls dressed in “Dirty Disco” outfits with “Don't tell daddy” on their bums. (Photo by Paul Jacobs/PictureExclusive.com)

A layer of morning mist still covers the fields as the sun rises into the morning sky over Hohenfelden, Thuringia state, Germany, early 07 September 2016. Meteorologists predict the weather to become warm and sunny in the region with temperatures reaching around 256 degrees Celsius. (Photo by Martin Schutt/EPA)

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)

Performers dressed as Pikachu, the popular animation Pokemon series character, perform in the Pikachu parade in Yokohama on August 7, 2016. Some 50 life-size Pikachu characters, the most famous from the Pokemon game, marched along the city’s waterfront street as visitors took mobile phone pictures and videos of them in scorching sunshine. Some participants said they attended the event to search for rare characters of Pokemon – a word short for “pocket monster” – for the megahit smartphone app, which was launched in several countries around the world last month. (Photo by Kazuhiro Nogi/AFP Photo)