A couple walk on a catwalk in a flooded Saint Mark Square during a period of seasonal high water in Venice on October 29, 2018. Venice frequently floods when high winds push in water from the lagoon, but Monday's levels are exceptional and forecast to rise even higher, to 160 centimeters (nearly 63 inches) by mid-afternoon. (Photo by Manuel Silvestri/Reuters)

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Lake Natron is a salt lake located in northern Tanzania, close to the Kenyan border, in the eastern branch of the East African Rift. The lake is fed by the Southern Ewaso Ng'iro River and also by mineral-rich hot springs. It is quite shallow, less than three meters (10 feet) deep, and varies in width depending on its water level, which changes due to high levels of evaporation, leaving concentrations of salt and other minerals, notably sodium carbonate (natron).

A military aircraft flies low through the Mach Loop in west-central Wales on September 25, 2025 during Cobra Warrior 25-2, one of Nato’s largest multinational air exercises. The operation, running across the UK until October 3, brings together air forces from the UK, US, Canada, Italy and Germany for three weeks of high-intensity training in challenging low-level environments. (Photo by Tony Marsh)

A woman wearing a scarf to cover her face looks on as she waits for a passenger bus on a smoggy morning in New Delhi, India, November 8, 2017. The Great Smog of Delhi is an ongoing severe air-pollution event in New Delhi and adjoining areas in the National Capital Territory of India, in November 2017. Air pollution at this time peaked on both PM 2.5 and PM 10 levels. It has been reported as one of the worst levels of air quality in Delhi since 1999. (Photo by Saumya Khandelwal/Reuters)

Erica Bougard of the U.S. competes in the high jump event of the women's heptathlon during the 15th IAAF World Championships at the National Stadium in Beijing, China, August 22, 2015. (Photo by Fabrizio Bensch/Reuters)

A humanoid dental patient robot, named Hanako Showa, about to be used during a demonstration of dental treatment at Showa University on March 25, 2010 in Tokyo, Japan. The robot was co-developed by the university and tmsuk co. Ltd, and simulates real human patients. The robot has been used for training of procedures in which the dental treatment requires a high level of precision. (Photo by Koichi Kamoshida/Getty Images)

241543903 (a.k.a “Heads in Freezers”) is a numerical keyword associated with a photo meme that involves people taking pictures with their heads in the freezer & sharing them online. By tagging a series of image files with a cryptic number, a high level of search engine optimization can be easily achieved. As a result, typing “241543903” into image search engines like Google Images successfully yields pages after pages of pictures showing people’s heads in freezers.

A tourist carries her luggage in a flooded St. Mark's Square, in Venice, Wednesday, November 13, 2019. The high-water mark hit 187 centimeters (74 inches) late Tuesday, Nov. 12, 2019, meaning more than 85% of the city was flooded. The highest level ever recorded was 194 centimeters (76 inches) during infamous flooding in 1966. (Photo by Luca Bruno/AP Photo)