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)

Employees wear "No-Face" masks during working hours at a service company in Handan, Hebei Province of China. As a service company, staff must smile to customers every day. On “No-Face Day”, staff wore masks to hide their facial expressions and allow them to relax. No-Face is a character in the 2001 animated movie “Spirited Away”, a silent masked creature who has no facial expressions.

Kendall Jenner (L) and Hailey Baldwin attend Harper's BAZAAR Celebration of “ICONS By Carine Roitfeld” at The Plaza Hotel presented by Infor, Laura Mercier, Stella Artois, FUJIFILM and SWAROVSKI on September 8, 2017 in New York City. (Photo by Bennett Raglin/Getty Images for Harper's BAZAAR)

Beyonce and Jay-Z leave Rihanna's 3rd Annual Diamond Ball at Cipriani Wall Street on September 14, 2017 in New York City. (Photo by James Devaney/GC Images)

A man walks past a neon soaked street scene mural titled “Belfast – Blurry Eyed” by Dan Kitchener, also known as DANK on March 1, 2018 in Belfast, Northern Ireland. (Photo by Charles McQuillan/Getty Images)

Beautiful seascapes capture the “raw power” of waves rising and crashing in the Indian Ocean. The stunning photos were taken off the coast of Durban in South Africa, and show formations from above and below the surface. Surfer and photographer Marck Botha took the images between April and July, and has always had a passion for the ocean. Here: Marck captured this moment in time from the shore on July, 30, 2015, in Durban, South Africa. (Photo by Marck Botha/Barcroft Media)

A woman holds an elderly woman on her back to cross a flooded street after a heavy rain in Shenyang, Liaoning province on July 14, 2017. (Photo by Fred Dufour/AFP Photo)

Aisha, 15, (L) (who asked to withhold her last name), a Syrian refugee from Raqqa, waits with a fellow refugee while harvesting cannabis in the Bekaa valley, Lebanon October 19, 2015. Syrian refugees work to harvest and process spiky-leafed cannabis plants in neighbouring Lebanon’s Bekaa Valley. Often farmers of cotton and wheat back home in Raqqa province – now the de facto capital of Islamic State – the conflict in Syria drove them to seek safety in a region where Syrian migrant workers used to spend a few months a year before returning home. (Photo by Alia Haju/Reuters)