Princess Charlene of Monaco and Prince Albert II of Monaco kiss on the balcony after the civil ceremony of the Royal Wedding of Prince Albert II of Monaco to Charlene Wittstock at the Prince's Palace on July 1, 2011 in Monaco. The ceremony took place in the Throne Room of the Prince's Palace of Monaco, followed by a religious ceremony to be conducted in the main courtyard of the Palace on July 2. With her marriage to the head of state of Principality of Monaco, Charlene Wittstock has/will become Princess consort of Monaco and gain the title, Princess Charlene of Monaco. Celebrations including concerts and firework displays are being held across several days, attended by a guest list of global celebrities and heads of state. (Photo by Pascal Le Segretain/Getty Images)

A fantasy figure promotes a video game at the Gamescom computer gaming fair in Cologne, Germany, Thursday, August 25, 2022. Around 1,100 exhibitors from 53 countries expect tens of thousands gaming enthusiast daily for the first time since the COVID-19 pandemic at the world's largest gaming event. (Photo by Martin Meissner/AP Photo)

Completion is near on Monaco's tallest skyscraper ever, and its first new one since the 1980s. Fueled by a luxury-housing boom in the tax-haven nation, the Odeon Tower's so-called Sky Penthouse is expected to sell for more than any other apartment in the world has ever sold before. Photo: The five-story Sky Penthouse is expected to be complete in September 2015. The water slide extends from a dance floor in the residence down to a private infinity pool. (Photo by Tour Odeon)

Enthusiasts gathered at Cad East in Snowdonia National Park, England to take pictures of F-15 Eagle fighters as they completed the Mach Loop, November 2017. (Photo by Caters News Agency)

“The World Stands on its Head” (“Die Welt Steht Kopf”) House on the Baltic Sea Island of Usedom stands nearly completed on September 3, 2008 in Trassenheide, Germany. The upside down house, complete with upside down interior furnishings, is the brainchild of Klaudiusz Golos and Sebastian Mikiciuk, and will become a local tourist attraction. (Photo by Sean Gallup/Getty Images)

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.

A tattoo of Captain America drawn by artist Sean Karon on the leg of client Ron Raucci at the Hampton Roads Tattoo Festival in Virginia, on March 2, 2012. The tattoo was completed from start to finish in one five-and-a-half hour session and won the prestigious “tattoo of the day” contest. (Photo by Jason Reed/Reuters)

Havilland Mosquito KA 114 performs a low pass during an airshow commemorating the completion of its rebuild on September 29, 2012 in Ardmore, New Zealand. The plane was restored by Warbird Restorations at Ardmore Aerodrome and is the only flying Mosquito in the world. (Photo by Simon Watts)