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 man rides his bike along a controversial bike lane on Prospect Park West on August 17, 2011 in the Brooklyn borough of New York City. In what is being viewed as a victory for the Bloomberg administration, a judge on Tuesday dismissed an effort by Brooklyn residents to remove a bicycle lane installed by the city on Prospect Park West. Mayor Michael Bloomberg, along with his transportation commissioner, Janette Sadik-Khan, has attempted to make New York more bicycle and pedestrian friendly with numerous bike and pedestrian lanes around New York City. The effort has angered some in the city who see the lanes as adding to traffic, taking up parking spaces and a danger to pedestrians. (Photo by Spencer Platt/Getty Images)

A Ka'apor Indian warrior (L) chases a logger who tried to escape after they captured him during a jungle expedition to search for and expel loggers from the Alto Turiacu Indian territory, near the Centro do Guilherme municipality in the northeast of Maranhao state in the Amazon basin, August 7, 2014. Tired of what they say is a lack of sufficient government assistance in keeping loggers off their land, the Ka'apor Indians, who along with four other tribes are the legal inhabitants and caretakers of the territory, have sent their warriors out to expel all loggers they find and set up monitoring camps in the areas that are being illegally exploited. (Photo by Lunae Parracho/Reuters)

A mechanic examines a Gogoro Smartscooter which is connected to a tablet, in its shop in Taipei, Taiwan, July 6, 2015. Companies such as electric motor scooter firm Gogoro could hold the key to Taiwan's economic growth. In just three years, the start-up raised $150 million to develop the smartphone-synched bike, and a charging network for it. Gogoro's success in creating a home-grown, innovative product is precisely what Taiwan's government wants to foster as it seeks to reduce the export-driven economy's reliance on the island's world-class tech manufacturing sector. (Photo by Pichi Chuang/Reuters)

These kaleidoscopic images are the work of one persistent photographer’s efforts to capture vibrant hues at the exact moment a wave breaks. Ryan Pernofski‘s stunning shots feature brilliant yellows, reds, blues and purples as an array of sunlight hits the water at the perfect time. What’s even more impressive: Ryan, a 27-year-old Australian, began shooting his popular masterpieces without using a professional camera, taking his iPhone out into the water instead. Ryan began experimenting with this method in 2012, using an underwater housing to protect his phone, as he could not afford a professional camera. (Photo by Ryan Pernoski/Caters News Agency)

The container ship NCL Salten ran aground at Byneset, outside Trondheim, Norway. A man in Norway woke up to find a massive container ship in his front garden. The 135-metre (443-foot) vessel missed Johan Helberg's house by a few metres at around 5am local time on Thursday, May 22, 2025 in Byneset, near Trondheim. Mr. Helberg was only made aware of the incident after his panicked neighbour, who had seen the ship heading straight for shore, repeatedly rang his doorbell and eventually called him on the phone. (Photo by South West News Service)

Two styles of cleaned bird's nest, Yan Zhan (L) and Su Zhan (R) await repacking at a processing plant in Kuala Lumpur, February 17, 2015. Prized in China for is alleged health benefits for hundreds of years, nests made from swiftlets' saliva are being mixed into coffee and cereal as the Southeast Asian producers of the delicacy seek to broaden its appeal, and their profit margins. The nests are among the world's most expensive foods, selling for up to $2,500 a kg and the swiftlets that weave them are indigenous to Indonesia, Malaysia, Thailand and Vietnam. (Photo by Olivia Harris/Reuters)

“eLEGS is a wearable, artificially intelligent, bionic device that enables people with paralysis to stand up and walk again. The exoskeleton is battery-powered and rechargeable, fitting comfortably and securely over clothing. Initially, eLEGS will be used under medical supervision for rehabilitation and training”. – BerkeleyBionics.com

Photo: Paralysis victim Stephanie Sablan (L) is helped by physical therapist Shonna Moran as she walks using eLEGS robotic legs at Santa Clara Valley Medical Center on May 25, 2011 in San Jose, California. Sablan, 24, was paralyzed from the waist down earlier this year when she was in a car accident and has begun using the newly developed eLEGS made by Berkeley Bionics. The robot-like battery powered eLEGS fit over clothing and enables people with paralysis to stand up and walk again. (Photo by Justin Sullivan/Getty Images)