The cave is 296 meters long, and consists of a series of twisting passages and chambers. The main passage varies from two to six meters high. The cave was formed through collapses following early karstic phenomena in the calcerous rock of Mount Vispieres. Around 13,000 years ago a rockfall sealed the cave's entrance preserving its contents until its eventual discovery which was caused by a nearby tree falling and disturbing the fallen rocks.Human occupation was limited to the cave mouth although paintings were created throughout the length of the cave. The artists used charcoal and ochre or haematite to create the images, often scratching or diluting these dyes to produce variances in intensity and creating an impression of chiaroscuro. They also exploited the natural contours in the cave walls to give a three-dimensional effect to their subjects. The Polychrome Ceiling is the most impressive feature showing a herd of bison in different poses, two horses, a large doe and a possible wild boar. The cave was excavated by Sautuola and archaeologist Juan Vilanova y Piera from the University of Madrid, resulting in a much acclaimed publication in 1880 which interpreted the paintings as Paleolithic in origin. Further excavation work on the cave was done by Hermilio Alcalde del Río in 1902-04, the German Hugo Obermaier in 1924-25 and finally by Joaquín González Echegaray in 1981. Scientists continue to evaluate the age of the cave artwork. In 2008, scientists utilizing Uranium-thorium dating estimate parts of the artworks are between 25,000 and 35,000 years old.
During the 1960s and 1970s, the paintings were being damaged by the carbon dioxide in the breath of the large number of visitors. Altamira was completely closed to the public in 1977, and reopened to limited access in 1982.A replica cave and museum were built nearby and completed in 2001 by Manuel Franquelo and Sven Nebel, reproducing the cave and its art. The replica allows a more comfortable view of the polychrome paintings of the main hall of the cave, as well as a selection of minor works. Several painters were influenced by the Altamira cave paintings. Some of the polychrome paintings at Altamira Cave are well known in Spanish popular culture.The song "The Caves of Altamira" appears on the 1976 album, The Royal Scam by jazz-rock band Steely Dan.
