Carbon dating cave paintings
First discovered in 1868, though not fully appreciated until the 1900s, Altamira was the first of the great caches of prehistoric art to be discovered, and despite other exciting finds in Cantabria and southern France, Altamira's paintings of bisons and other wild mammals are still the most vividly coloured and visually powerful examples of Paleolithic art and culture to be found on the continent of Europe.
As usual, archeologists remain undecided about when Altamira's parietal art was first created.
The actual subterranean complex itself consists of a 270-metre long series of twisting passages ranging from 2-6 metres (about 7-20 feet) in height, in which more than 100 animal figures are depicted.
Unlike most other decorated rock shelters of the Upper Paleolithic, Altamira cave was a place of domestic human habitation This was limited to the cave mouth and lobby area, although paintings and petroglyphs were created throughout the length of the cave.
For four decades thereafter Altamira was the world's leading showcase of prehistoric ancient art, until its eclipse by the Lascaux cave paintings in the late 1940s.
The first significant research into the age of Altamira's rock art was done by French paleolithic scholars Andre Leroi-Gourhan and Annette Laming.
However not until the anthropologist Henri Breuil (1877-1961) began circulating copies of the paintings in the mid/late 1900s, did the world at large became aware of the true visual significance of the site.
But the main discovery was an eighth level, previously undetected, dating back to the Gravettian era of about 20,000 BCE.
Then, in 2008, British scientists dated the paintings using the Uranium/Thorium (U/Th) method.
It was closed for conservation purposes in 1977 (reopened 1982), and again in 2002.
Today, the cave is only accessible to scientists and a handful of visitors chosen by lottery.