Meantime, the Spanish Ministry of Culture has opened a replica cave at the adjacent National Museum and Research Center of Altamira.Other replicas can be seen in the National Archeological Museum of Spain, Madrid, and in the Deutsches Museum, Munich.

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.

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.

Experts who read the report, notably the French scholars Gabriel de Mortillet and Emile Cartailhac, ridiculed its findings at the 1880 Prehistorical Congress in Lisbon, although eventually, in 1902, they and other scientists in the archeological establishment admitted their mistake and acknowledged the authenticity of the Altamira paintings.

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.

In 1985, Altamira was declared a UNESCO World Heritage site.

In 2008, UNESCO added 17 additional caves to the Altamira World Heritage Site.

However, he also exhibited oil paintings at the Royal Academy, the British Institution and the Society of British Artists.