A woman rides a donkey during a donkey race in Roum village, Jizeen countryside, southern Lebanon, August 9, 2015. (Photo by Ali Hashisho/Reuters)

A model poses with a motorcycle and a car on a racing track at the Essen Motor Show in Essen, Germany, November 27, 2015. (Photo by Ina Fassbender/Reuters)

Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

Participants run through coloured powder during the Colour Run race in Moscow, Russia on June 5, 2022. (Photo by Maxim Shemetov/Reuters)

A couple participates in the “Running of the Brides” race in a park in Bangkok, Thailand on March 25, 2017. (Photo by Athit Perawongmetha/Reuters)

A man dressed as Santa Claus sits at a bus stop before an annual race in Belgrade, Serbia December 27, 2015. (Photo by Marko Djurica/Reuters)

A cenote is a natural phenomenon, a sinkhole in the Earth’s surface. The Yucatan Peninsula in Mexico has an estimated 7,000 cenotes because it is primarily made up of porous limestone. For millions of years, rainfall slowly ate away at the limestone and a huge system of underground caves and caverns was formed. Many filled with water from rain or from the underground water table. When the roof of a water filled cave collapses, a cenote is born. The water found in a cenote may be fresh water, salt water, or both. Structurally it may be completely open, like a lake, almost completely closed with just a small opening at the top, or somewhere in between.

Racing fans soak up the sunshine and dress to impress during Ladies Day at the Aintree Grand National meeting on April 8, 2011 in Aintree, England. Friday is traditionally Ladies day at the three-day meeting of the world famous Grand National, where fashion is as important as the racing.