People look on as water from the rising Mississippi River is released through the Bonnet Carre Spillway while washing out a road May 9, 2011 in Norco, Louisiana. The Army Corps of Engineers began redirecting part of the Mississippi River through the spillway today to lower river levels and reduce pressure on levees in order to avoid a catastrophic failure. The water will flow nearly 6 miles north before emptying into Lake Pontchartrain as the Mississippi rises close to the highest level ever upriver in Memphis. (Photo by Mario Tama/Getty Images)

People use snowshoes during a tour of the Great Kemeri Bog, Latvia, October 17, 2015. The Kemeri bog is more than 8,000 years old and is one of the largest dry moss swamps in the Baltics. A more than decade-long joint restoration of the bog by the European Union and the Latvian government helped the bog recover its high moss marshes, damp black alder forests, floodplain meadows and seaside lakes – features now considered rare in Europe due to industrialisation. (Photo by Ints Kalnins/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.

“Artist of the light”. While shooting sunrise in the Vermilion lakes area of Banff national park, Canada, I met a fellow photographer on the scene. Most of the time, we tried not to get in each other's way, however, just by accident, I snapped a picture with him in it working on his tripod settings, and it turned out to be a great photo compared to my sunrise shots. (Photo and caption by Victor Liu/National Geographic Traveler Photo Contest)

ATTENTION! All pictures are presented in high resolution. To see Hi-Res images – just TWICE click on any picture. In other words, click small picture – opens the BIG picture. Click BIG picture – opens VERY BIG picture.

The carcass of a yacare caiman lies in the dried-up river bed of the Pilcomayo river in Boqueron, Paraguay, August 14, 2016. In Paraguay, alongside the Pilcomayo River, black vultures flew over a shrinking pond where a group of crocodilian reptiles known as yacare caimans sought refuge. Water from the river, which divides Paraguay and Argentina in the area of the Gran Chaco, was scarce. This is not an uncommon sight in the region of General Diaz, about 700 kilometres (435 miles) northwest of the country's capital Asuncion, where the Pilcomayo's waters form lakes and streams that give life to capybaras, birds and caimans. (Photo by Jorge Adorno/Reuters)

An adult female Masai giraffe rears on its hind legs as it resists efforts by Kenya Wildlife Services (KWS) rangers to guide it into a transportation crate using ropes during an exercise to translocate large herbivores from Kedong Ranch due to land subdivisions and corralling that have disrupted wildlife migratory routes in Naivasha, Nakuru County, on November 16, 2025. Driven by two long ropes held by about twenty rangers, the blindfolded giraffe enters a tall trailer that is to transport it out of its natural habitat in the Rift Valley, which is deteriorating after having been resold. This is the first step in a meticulous relocation operation in the vast Kedong ranch, part of an ancestral corridor between Mount Longonot and Hell's Gate Park, near the iconic Lake Naivasha. (Photo by Tony Karumba/AFP Photo)

A woman dressed in a dirndl, a kind of traditional Bavarian clothing, jumps into Lake Schlier on July 30, 2006 in Schliersee, Germany. The event called "Dirndlfliegen" ("Dirndl Flying") was sponsored by a local fashion store and a big Austrian Dirndl manufacturer. While these kind of events had been held in Austria before, this was the first of its kind in Germany. 29 women and one man wearing a wig participated in the event that held a new Dirndl as the grand prize. (Photo by Andreas Leder/Getty Images)