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A gigantic network of passages, canals, fissures and caverns runs through the limestone soil of the Yucatan Peninsula in Eastern Mexico. Experts consider it to be the world’s largest continuous cave system. It stretches over hundreds of kilometres – even until today, nobody knows exactly how long it is.

Falling sea levels during the ice age exposed the carbonate rock layer, causing intensive karstification and weathering processes, such as dissolving, of the rock below the surface to begin. Karstification also explains why there are almost no rivers or lakes in the northern part of the peninsula. Precipitation drainage in the area mainly takes place underground through an extensive cave system. On the surface, however, the karst nature of the landscape is visible from a great distance due to numerous shaft-like sinkholes in the ceilings of limestone caves – the so-called “cenotes”. The term is derived from the Mayan word “ts`onot”, which means “sacred well”. The streams of water flowing underground are accessible by means of these cenotes. Over 3,000 cenotes can be found in Yucatan, which were already of great significance for people during prehistoric times.

Fire sites and human bones, discovered by underwater archaeologists during dives in the vast expanse of labyrinths, testify to this fact. The Leibniz-Laboratory for Radiometric Dating and Isotope Research in Kiel determined the age of the charcoal remains of these fires to be 8,400 years. This caused the previously estimated date of arrival of the first immigrants to the peninsula to be moved considerably further forward.

Flows leads you on a journey never before taken, exploring the aquifer on the
Yucatan Peninsula in Mexico. Flows will show you unique footage from the air and
underwater, taking you more than a kilometre into a submerged cave system to
see the incredible mirror mirage where salt and fresh water meets and much
more. Music in Flows is by Thom Yorke.

The film provides a diverse mix of visually stunning scenes including coral and
barrier reefs, aquatic animal species, the expansive underwater river system, Sian
Ka’an Marine Reserve, tropical mangrove forests, and the ocean juxtaposed with
the challenges of construction, tourism, unsustainable development and

An open fire in the caves was quite possible at that time, as sea level was approximately 65 metres lower than today. The underground labyrinth, therefore, previously formed by rainwater runoff, was dry in the past, as the stalactites and stalagmites in the crystal clear water show today. After the end of the last ice age, the glaciers melted and water flooded the caves, preserving the relicts of the past. The temperature in the caves was a constant 26 degrees, the water current was weak and it was completely dark.

The water level of the cenotes was high, even during the classical Maya period, as this level is dependent on the sea level. The cenotes were essential to the Mayan people for survival, as Yucatan has very few notable rivers. They did not only derive their drinking water from the cenotes, however. They also threw offerings for their gods – both dead and alive - into the deep holes. Over 120 human skeletons were found in one cenote – the largest cenote in the town of Chichén Itzá.

In co-operation with theInstituto National de Antropología e Historia(National Institute of Anthropology and History, INAH), underwater archaeologists from theArbeitsgruppe für maritime und limnische Archäologie(AMLA) from the Institute for Prehistory and Ancient History at the Christian-Albrechts-Universität Kiel have been researching flooded cave systems and cenotes (collapse dolines) in the northern part of the Yucatan peninsula in Mexico since the summer of 2009.

The research divers from Kiel bring the necessary expertise for these complex dives. The co-operation with their Mexican colleagues aims at gathering, researching and preserving archaeological finds and features from different historical periods from the extensive cave systems of the Yucatan and Quintana Roo states. Abundant finds have already been documented since the beginning of the investigations, including bones from fauna in the glacial period, prehistoric fire sites and burials, as well as religious and secular remains of the Mayan people.

Although the cenotes are the focus of the investigations of Florian Huber’s (AMLA) archaeological research team, a detour to Isla Contoy is also part of the work programme. The research divers will obtain an overview of the deposits of significant artefacts from the various historical epochs, in the marine waters around the Isla Contoy National Park.

Stalactites and stalagmites in the large cavern of the Toh Ha cave system
Stalactites and stalagmites in the large cavern of the Toh Ha cave system (Photo: U.Kunz)
Offerings from the Mayan period
Offerings from the Mayan period (Photo: U.Kunz)

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